Silk and fine wool provide warmth with minimal bulk. I personally hate being cold and agree that it is sensible to find an appropriate garment to provide sufficient warmth with elegance. Since you saved so much in the dress, splurge on a great WARM wrap that will keep you toasty and allow you freedom of mivement. Goosebumps from cold are uncomfortable and unflattering.
A benefit of a wrap instead of a jacket or shrug is ease of taking off and on as wanted.
If you are worried about whiteness, try the Hollywood route and get a fake tan. You can try one ahead of time to see if you like the look. Just don’t use the person Trump uses. For a guy with so much supposed $, you’d think he could get a better fake tan.
A cashmere or pashmina wrap (woolen) might be a good investment. Something you can use even after the wedding. What I like about them is that they are so lightweight and warm and fit in my handbag. I know Nordstroms sells some nice ones. I am thinking that you might be wearing it at times at the wedding but there would be times when you may remove it. I too would feel cold in something sleeveless in the winter and a wrap or shawl (something light) would keep my arms warm. The issue maybe that you might want your photographs to be focused on the dress you are wearing rather than covered up with something else.
I am beginning to think about a white silk undergarment, like I use to wear when I skied. Not a turtle neck, but something u shaped that the dressmaker could modify.
That royal blue dress you got is very pretty. I love the lace on the back of the dress. It is really beautiful and very elegant. It would be nice if there was a way to find matching lace like the back to make a light lace jacket that would cover your arms that you could wear over it. Lace sleeves would be semi transparent but it wouldn’t really feel like a heavy jacket covering the dress. I wonder if online we could find a royal blue lace jacket that could go with the dress. Maybe something like this.
http://www1.macys.com/shop/product/guess-collena-zip-front-lace-jacket?ID=2843608&CategoryID=120&swatchColor=New
Maybe I’m the only one, but I prefer the $50 Macy’s dress with the little lace jacket. And it gives her a jacket! No need to go wrap shopping.
ETA - I swear I looked at it yesterday and it was $50. Now it’s back up again! Must have been a Labor Day special. Geez, this stuff will drive you crazy.
http://www1.macys.com/shop/product/alex-evenings-petite-sleeveless-glitter-gown-jacket?ID=838610
@greenwitch - Yes, I got that one (on the way) for $89.50. On it’s way! It’s going to be like a little dress shop here!
This is the dress I bought for my daughter’s wedding. I want sleeves, I like the color and she likes it. Done. 
silly idea but could a seamstress attach some sleeves? I know it would be a shot in the dark to see if you could find some chiffon or lace to match but just a thought.
@cap, I love that dress.
@cap - I love that dress! That’s sort of what I was looking for only in a different color and a long skirt.
@walkinghome that dress you ordered is similar. See what you think when it arrives. Try both dresses on…walk around your house. Have someone take a pic of you in both. They are both very pretty.
I do love the royal blue one…but understand your concern about being cold. OTOH…as mother of the bride, can you ask the vendor to set the heat a tad higher?
Then everyone else will roast! No! 
I definitely second thumper’s suggestion to try on the dresses, walk around in them, have someone take a picture of you in them. I went through this last year. I could’ve opened a MOG dress dept for all the dresses delivered to my house. When it came down to decding between 2 dresses, the pictures DH took of me in them helped decide. One dress was very nice IRL, but didn’t show as well in pictures as the other dress.
I’ve gotten some dresses and I believe I have a winner: http://www1.macys.com/shop/product/alex-evenings-petite-sleeveless-glitter-gown-jacket?ID=838610&cm_mmc=OpsEmail--264_multi_ship_confirmation--838610-_-MB Fits well, the jacket is lightweight and sparkly. This was the only petite that I ordered and it did make a difference. The waist and shoulders are where they are supposed to be and it will only need to be hemmed an inch or two. The other ones were 6-8" too long and didn’t quite fit at the shoulders or waist. If you look at the picture though, you’ll see on the model it’s a mid-calf. On me, it’s very full length - which is okay. Cost was $89.50, so not too bad!
It’s a beautiful dress! Love the flow of it.
But I’d still keep,that royal blue one. It’s so pretty.
Nice dress. Great price!
Very attractive choice, @walkinghome, and provides the arm coverage you were looking for with less hassle than other options.
Perfect!
It’s so nice when a dress fits without needing any alterations–congrats on finding a perfect dress and fit at a great price! 