It never would have occurred to me to invite my bridesmaids, much less my MIL to be! For one thing, I really didn’t want my friends to have a sense of what my parents could afford and were willing to pay for a dress - as that was none of their business and could have been quite awkward.
My daughter had me, her sister (maid of honor), one of her bridesmaids, and her future mother-in-law. She tried on several dresses, but when she tried on “the one” we all knew it immediately. No worries about expressing opinions whatsoever - I don’t think any of us could have said anything but “oh my gosh - yes.” (I got tears in my eyes.) Nice bonding experience for us all. Future MIL took us all (small group) out to lunch afterwards as a thank you for getting included.
So jealous–with three boys (and one already married) I’m not sure I’ll ever get this experience, so I watch “Say Yes to the Dress” episodes! Enjoy the girliness, bring tissues, and remember it’s about what the bride wants. Have fun!!!
My D bought her wedding dress online. Hope her future MIL wasn’t too disappointed I raised a practical daughter! If only I could have convinced her to elope… An afternoon with 8 people looking at dresses sounds awful to me.
She’ll get lots of opinions from her 3 older sisters, so stay positive, have fun, and enjoy the experience.
I remember my dress shopping expedition at the NYC Bridal Building, open to the public on Saturday only. I had one friend. The place was packed with groups of up to what looked like 15+, all squabbling loudly. Argh. The place had about 20 floors and one elevator, and a big line to get in and use it. We walked up, LOL.
Sounds like you will have fun, though. Hopefully the sisters will restrain themselves. Make sure to share your behavioral cautions with your D. 
Enjoy!
My future DIL invited just her mother and me to her dress choosing session. Re Pizzagirl’s concern re money coming up, I was not exposed to that aspect – assume the gown price was shared with the bride in the dressing room, and she and her mom handled payment at the counter at the end of the process, and I did not go there. So I do not see that as an issue at all. I assume bride and mom had discussed price in advance and bride limited what she was shown to a certain price range. (She is a very sensible young lady.)
When DIL came out in “the” dress, it was another of those unanimous reactions. I had tried to be quiet during most of the process, would not have made negative comments re any gown, but knew her taste, plus she had been pretty clear in advance re what she wanted.
I gave little but positive input overall but when she expressed concern about whether she should look more, just “in case” there was another gown somewhere she would like even more, I did respond. (Basically, I commented that the gown type she wanted was a small percentage of what is generally available, she had found a gown that met her criteria and she was very happy with, she is very busy in professional school, and the odds were high that she would still prefer the gown she had found that day even if she looked lots more.)
Her mom told me after that I had been very helpful. All three of us felt that the gown she chose “matched” her style and worked well for her. So it was one and done. I expressed appreciation many times for being included, took pics of her in the gown including some with her mom, and e-mailed them to them.
Overall, a very positive experience for which I am very grateful.
P.S. Ironically, I did not attend a gown try-on session with my own D, who lived and was married in a city six hours away, and ended up choosing a gown online that worked well for her.
How lovely that you were invited to share the day. I think you got it right – just smile broadly and say everything looks wonderful. I would also be sure let your future DIL as well as her family know how much you appreciate being included. A pack of kleenex and some mints in your pocketbook might be a good idea (although the store likely has tissues on hand). I’d stay away from taking photos with your phone/camera so your son won’t be tempted to sneak a peek.
When I go shopping with friends, I like to make short videos of the person walking toward me and away from me in whatever it is–you’d be amazed how much looking at how you look when you’re actually moving in clothing changes your opinion of it. Mirrors and a front-only view just aren’t the same.
D’s maid of honor accompanied me and D when she shopped for her dress. She was not looking at the price tags and did not hang around while I paid the deposit so she had no idea what the dress cost.
I would not assume that having multiple people means a lot of opinions and drama. That’s what they like to show on the reality series, but not necessarily what happens in real life. D, her MOH and 4 bridesmaids selected their dresses in 20 minutes, agreed on everything and absolutely no drama involved.
@abasket, How thoughtful of her to invite you given that she will already have lots of support in her family. My lovely SIL was a bit disappointed not to have been part of the wedding dress fun when her son married.
And I agree with FallGirl, it’s always good to be ready to “just nod and smile,” but major holding back probably won’t be necessary.
Congratulations, enjoy the joyous occasion – AND TELL US ALL ABOUT IT. Details!! We want details !!
“Re Pizzagirl’s concern re money coming up, I was not exposed to that aspect – assume the gown price was shared with the bride in the dressing room, and she and her mom handled payment at the counter at the end of the process, and I did not go there”
I bought my dress at either Neiman-Marcus or Saks, I don’t remember which. I was with my parents who were footing the bill. My parents said the budget was $x, which was perfectly fine with me. I tried on dresses in that price range; very nice. The salesperson said “this is above your price range but I think you might like it.” I tried it on, I emerged from the dressing room and my father had tears in his eyes and said “that’s it, wrap it up.” It was actually close to 2x but my parents were quite spendy. I really don’t think I would have wanted my 21 yo bridesmaids, esp those with student loans/debt who couldn’t remotely afford this kind of thing, see that. It really would have been awkward. We chose modest cost outfits for them and paid for a lot of their expenses including putting them up for the weekend, but it really could have come across as awkward to “watch me shop at Neiman’s.” Having said that, abasket should go and have herself a blast! Maybe bring small bottles of water in addition to Kleenex and mints?
I will be happy to tell you about the experience afterwards! So interesting to hear everyone’s opinions and past scenarios.
I think I see my job in life to be the glass half full person, so I’m sure this event will be no different! She is beautiful - inside and out - if she puts a paper sack on and loves it, I will say “SO DO I!!!” 
What a thoughtful DIL you are getting! I am also the mother of boys and may not get that experience, although I have heard about this custom more frequently in recent years. I’d suggest that you say every dress is perfect…compliment the bride frequently (sincere compliments, obviously)and be uber gracious. I’m sure you are a gracious person by nature!!
Not sure if it would work with your crowd, but could you spring for mimosas or similar refreshment since the store will be closed to others…might be a small way to repay the courtesy to the bride and her family. Most of all, have fun!
You know what I love about this? Here we are, parents (mostly mothers) of accomplished young adults, accomplished adults in our own right, getting all girly about this stuff!!
I thought it was funny, all these years later, to hear how my SIL didn’t like her future DIL’s dress. There was nothing wrong with it, of course, and my now-niece looked absolutely gorgeous, but it wasn’t as traditional as my SIL preferred. The dress looked very much like Carolyn Bessette’s wedding dress when she married John John.
ETA: That’s a long link!!!
@VeryHappy – there’s something about wedding dresses! (And I’m one who had a modest wedding and a simple white dress it took me 30 minutes to select off the rack at Macy’s!)
My daughter is a scientist. When she goes on vacation, she roughs it in out-of-the-way places with no toilets and often no electricity. She rock climbs. She scales 14,000+ foot mountains.
You know what her favorite TV show is? “Say Yes to the Dress.” She tapes and binges. She even got me to join her.
My boys watch with me when we are at my parents’ house, which has cable.
Are they single, Youdont’say?
My DIL invited me to go with her for her first time wedding dress shopping. Her mom lived in another country, so she couldn’t attend. It was just me and one bridesmaid and we went to a chain store that DIL choose. We had a dreadful experience and she came home very defeated. She wanted a style that wasn’t very popular (she wanted coverage for her shoulders when strapless dresses were at the height of fashion) and she had a very small budget (small for a wedding dress). So, slim pickings.
Anyway, I felt so sad for her and seeing her so dejected from wedding dress shopping - what should be a happy time. So, I said to her, next weekend we’ll go again and I’ll arrange where we’ll go. She perked up immediatley and so I began to plan. I had no idea what I was doing (I wore my mom’s dress so I never went shopping for The Dress) but determined to figure it out. At the first place we went to that next time, the lady greeted us at the store and asked if we had an appointment. Oops! It never occurred to me that this was necessary. She said that there was a 30 min window of time before the next appointment so why not discuss what she’d like and then she’d put together a few dresses for hte next visit. After hearing her desire (a non-strapless dress) for the wedding dress, she said that she only had one dress that fit her wishes. She tried it on and Oh My. It was The Dress. It fit her as if it was made for her body. It was perfect. Then we looked at the price. Gulp. It was above her budget. So, I stepped in and sincerely thanked the salesperson but noted that it was above budget.
She said to wait a minute. Then the owner came out and we spoke. She connected with my DIL - being in a new country without any family. She had had that experience many years earlier. She lowered the price and made my DIL a very happy young lady!
My DIL could not stop smiling. We went back to my house and watched Seven Brides for Seven Brothers - a perfect movie to watch after wedding dress shopping. And my DIL and I had a good bonding experience.
A win for everyone.