I called my in laws Mr and Mrs when I was dating… after marriage I couldn’t change to first names and no way I could use mom and dad. So I didn’t ever address them directly which was super awkward and I did everything I could to make sure no one ever noticed. Having kids was the best thing because then they became Grandma and Grandpa. 
I can’t stand being called Mrs by anyone. First names for me!
We also did the avoid calling the in-laws by any name unless absolutely necessary.
DH and I called our in-laws by their first names. From this thread, I realized that my DSs’ GFs don’t really call us anything. I am fine with them calling us by our first names. My cousin’s wife called her MIL “mom” especially when MIL moved in with them and I have heard some others refer to in-laws as mom and dad. I might be OK with that, but not near that point yet.
My FIL used to sign cards “Dad/first name/Grandpa” to cover all of us I guess! If my parents wrote a card to both of us, signed it mom and dad.
My kids SO’s call us by our first names. They were adults when we were introduced and all adults call us by our first names, even the kids’ friends who’ve we’ve know since they were in kindergarten have mostly transitioned to first names. I dated H for 5 years before marriage, I was finally allowed to call them by their first names after the wedding (they also said mom and dad would be fine but I preferred first names, H has been calling my parents by their first names day one). He’s mom is actually his stepmom, he calls her mom but his sisters call her by her first name. So for 5 years, his step siblings called his dad by his first name, siblings called his mom by her first name, and I was literally the only person calling them Mr. and Mrs. H’s siblings we’re all married when we started dating, he was the youngest by far.
For our parents, we used Mr and Mrs until we got married. My parents were Mom and Dad, though sometimes DH used a first name to grab attention; DHs parents were Ma and Da.
My kids’ SOs call me by my first name - it’s how I introduced myself to them.
ETA My siblings and I still refer to our parents as Mommy and Daddy in conversation, as in remember when Mommy… have you spoken with Daddy…
Yes, PLEASE have the light conversation with your DIL and address the subject - she will be glad you did!
For all the time I was dating/married to H and all the years they were alive we never had that conversation and I avoided calling them…anything… I actually always felt so awkward about it. With H I would say “your mom” or “your dad” but I always wished they would give me permission to use their first names - or whatever!
My kids call me mom and H dad but both of us have a “nickname” that has stuck since the kids were little and played imaginary games - everyone in the family had a nickname - and they have stuck so that we use them on occasion for everyone! To be honest, I think that might end up being my grandparent name if offspring every happen!
26 year old daughter will sometimes refer to me as “mommy” or “Mother” or even “abasket” - like just on occasion and it’s situational. I would not care if they called me by my first name - it IS my name - and it doesn’t change being “mom”!!!
Yes, mid-20 year olds who call their parents Mommy and Daddy exist. My kids, for example😉. To us, it’s affectionate and respectful.
My mother called her parents Mommy and Daddy until they died when she was in her 50s.
If all parties to the relationship embrace the name, it’s all good.
DIL calls us mom and dad. We just told her she was welcome to IF she was comfortable doing so (or alternatively first names or any variation really). She quickly picked it up with no hesitation. After years of calling my in-laws “hey you!” and avoiding calling them anything it is a welcome relief.
I did this for 10+ years to my in-laws. Just really no names. When we had kids they got their grandparents names.
We have a ‘bonus’ daughter (D19 roommate from college) who is part of the family. She has odd family setup being estranged from her mom and her bio-dad never around. She is just part of the family for the most part. She is in on the family groupchat. She has spent holidays and vacations with us. Once they graduated she has started to call us by our first names, but in some ways we all agree it sounds weird. Great kid and great friend to D19.
The weirdest thing though is her Ex-Stepdad is somewhat still around and in her life to a degree. He and her mom got divorced at some point. Well the ex-stepdad is loaded and I mean serious money. I only bring that up because he has taken D19 and Bonus daughter on some great trips in the last year. I am talking Napa Valley and Michelin Star restaurants along with VIP day at Disneyland. A quick NYE trip to LV. D19 has gotten a peak to seeing how the 1% live. Nice guy. He came out to graduation. I just think he is bored because he never had any of his own children and his finance passed away from cancer about 2 years ago.
My daughters call me Mommy.
My S’s (21 and 24) have mostly shifted from calling me mommy to momma. But there are times in quick conversation that Mommy comes out.
One such dinner included my niece who gasped and said “Did you really just call her Mommy? That’s weird.” My response to her was (and would be to anyone): “As long as they keep talking to me, I’ll answer to any name they use.” She was very quiet after that. And we kept talking.
My kids call me mommy. I called my dad daddy. My DIL calls us by name. My DD’s SO first call us Mr and Mrs and then we tell to call us by first names
We are first names with all the spouses and have been since we first met them. My in-laws have always said I could call them Mom and Dad but I wasn’t comfortable with that. I tend to call the grandma and grandpa when the kids are around otherwise I try not to call them anything. With my husband I refer to them as your mom and your dad. My older siblings refer to our Dad as Daddy. I don’t know when I made the switch.
Our kids call us Mother and Father which is so weird, a little cringe and very “mother dearest” 
I think they started it as a joke and somehow it stuck. We have always referred to each other as Mommy and Daddy when talking to the kids and they say Mom and Dad when talking to friends. But definitely Mother and Father when talking to each other. I am used to it now.
ETA - I think the joke is on me because I have a set of sibling friends who only refer to their parents as Mother and Father and I always rolled my eyes feeling it was SO old money snobbish of them.
Miss First Name.
Wow.
My in laws insisted on being Mom and Dad, and though it was a little awkward at first, I’m really glad they did.
We referred to each other’s parent(s) by their first names. Our children call us “Mom and Dad.” Our SIL and #2D’s long term BF call us by our first names.
When I was growing up, I had a lot of aunties, none of whom were actually related. One of my mom’s best friends had us call her by her first name, while her husband insisted on Mr Last Name. He was that until the day he died.
When my now 35 yo niece was tiny, she started calling her parents by their first names because that’s how they referred to each other. It soon became mommy and daddy, although they didn’t call each other that.
Our son in law calls us by our first names.
Our kids call us mom and dad. Always have.
Definitely my first name. I have always asked my kids’ friends to call me by my first name too. I would never want to be called Mom by anyone by my kids. Makes my skin crawl to think about it, honestly, like the married couple that calls each other Mommy and Daddy. Not my thing.
I call my mother-in-law by her name or by her grandparent name depending on the situation (mainly if the kids are present).
My kids call me “Mom” or “Madre” (they took Spanish as their foreign language). Maybe occasionally they might say Mama, but I think it’s mostly Mom, or just “hey you did you buy any food at the store?”
You must not live in the South. I called my dad Daddy until the day he died and my mom Mama until she died. That’s totally normal here.
Incidentally Mami (pr Mommy) is common amongst Spanish speakers too.