So. I thought FMIL was out of hand, I guess I was wrong.
Here's the story...I am only having 3 children at my wedding, those part of the wedding party. One flower girl is my niece (Flower Girl A), my sister mentioned that she was going to bring a separate dinner because (FG A) is a picky eater (doesn't want her to just eat dessert) I think, oh that's a good idea! She doesn't like a lot of food and will want to fill up on sweets, this way if there's a food battle with whats on the menu then my sister has a back up meal. Other flower girl is FI's cousin's daughter (Flower Girl B ). I contact FI's cousin "Hey, my sister is bringing an extra dinner for (FG A) because she is a picky eater. I was wondering if you think (FG B ) will like the food on the menu for dinner or if you wanted to do the same. Convo continues...Menu is salmon, filet mignon and chicken parmesan. I explicitly say word for word "I know the kids will enjoy the appetizers and desserts. I was just wondering about dinner" no response.
Cousin calls her dad, who calls his bother, who then calls FMIL..."Did you say that (FG B ) won't be allowed to eat at the wedding?! *Face Palm*
Looking back, I could have worded it better. Or maybe I should have never mentioned it at all. I'm guessing the latter. I'm just astounded that there was a game of telephone that went terribly wrong and now the family is "up in arms"
Dramatic. No?

Re: Out of hand miscommunication
Can you ask your caterer about kids' meals? Even if you're only having three children, guests really shouldn't have to provide their own food, with a few exceptions. (ie. I eat mostly vegan, so I usually bring a snack in my purse.) With that being said, do you also have a vegetarian option for dinner? What are the sides?
My FMIL called screaming. She mentioned that the family is "up in arms" about the situation and everyone is mad that I didn't "volunteer myself to get chicken nuggets for FG B to eat".
I guess I was surprised that the convo had to go through so many people and there was no attempt to "solve" the issue, only complain. I mean, aren't we all adults? We can talk to each other right?
I do have a vegetarian option at the wedding, there is side options of roasted potatoes and eggplant rollatini and the caterer does not have kids meals as an option. I don't think the food on the menu is unique enough that a child won't touch it. I just know my niece is exceptionally picky, I was trying to extend that info to the other mom in case she has a similar picky eater. Of course, I am not barring her from eating, I just didn't want the kid to go hungry if she didn't like anything.
ETA: At this point, I would contact the cousin directly, let her know her daughter is welcome to eat anything on the adult menu but she can bring something else if she wants, and consider the matter closed.
Sorry, I didn't think you were getting that impression. I over-explain at times.
I will make sure to do that. I def don't want anything going out of hand. Thank you for the advice.
I agree with @ahoywedding. It is too bad and frustrating that such a simple misunderstanding got out of hand.
Too late now, but I wouldn't have said anything to the cousin to begin with, unless you were calling to get her daughter's dinner choice anyway.
I'm assuming you already explained the misunderstanding to your FMIL.
Back to the cousin. I'd call her up and apologize for the misunderstanding. Something like, "Cousin A, I just heard from MIL and I am so sorry that I wasn't clearer and there's been a misunderstanding about FG B's dinner! Of course we will be providing her with a meal from our caterer, if that is your all's preference! The entrée choices are salmon, filet mignon, and chicken parm. Just let me know which one she prefers with your RSVP. There will also be lots of yummy appetizers and desserts."
At this point, I'd make the assumption they want dinner for their daughter and just let it go. If she actually has the gall to respond back that she wants chicken nuggets for her daughter (like your FMIL mentioned), I'd explain that you've already checked with your caterer and unfortunately they don't have any children's meals to provide.
As an aside, FFS, what do they think chicken parm. is? It's a fried chicken breast. Without the sauce and cut into pieces. Boom. It's chicken damn nuggets.
I'd then offer to request that the caterer leave the sauce off the chicken parm. for the little girl. And her parents can cut it into whatever nuggets, strips, or shapes they frickin' want (more eye roll).
I wouldn't have asked because kids should be able to eat that menu. Maybe this is an unpopular opinion, but I dont believe in giving kids separate meals. There's no reason to have a kids meal, and if someone is that picky, they can bring their own upon seeing the menu card.
Also, i think the cousin is crazy to interpret your convo that way and then play a game of telephone with Mom, Dad and great aunt Mary of your second cousin getting back to you.
FI's cousin responded she could not predict what FG B would eat. I asked her what she usually likes, maybe the caterer had something similar on the menu, and I apologized for the miscommunication and reiterated that my goal was to make sure everyone had a meal. Seemed to go well, but I guess I won't find out until there's another random phone call from a family member.
I do agree that children are capable of eating "adult food" it is not so unique that a child would not touch it.
I think it's time for a glass of wine.
Good you clarified what you meant, and leave it at that.
The cousin creating a game of telephone and not responding to your directly is more obnoxious to me than your FMIL's screaming tone. Although both are bad. Ditto PP I'd do a brief apology and explanation but drop the subject after that. It was nice of you to reach out at all- other than an allergy or religious observance, I feel that guests' issues with food should be between them and the kitchen.
I would have taken your phone call re: FG B very rudely also. I would have interpreted it as you saying "I assume what we're serving isn't acceptable to you, but I don't care. You should bring something else, since you're such a pain in the ass and clearly would throw a fit if you didn't have exactly what you wanted". Now, obviously that's not what you meant! Your heart was in the right place, but it came across wrong. I absolutely think you need to apologize and explain what you really meant.