OP here. Trust me. It is not a joy dealing with our picky DS. *I am so looking forward to not having to worry what she'll eat, will she like it or will she whine about it. *She is opposite of our DS. *Go figure. . *
Just to let you know I empathize completely. Our girls are 11 and 4, and exactly like your two. Last year at Yachtsman, they switched meals so oldest could have a kids meal and youngest had steak. Our oldest also regressed as she got older. There are many chicken strips she won't eat because of the heavy, bumpy breading. No red meat or pork, chicken breast only if plain and grilled, she can't do anything lumpy like smoothies or juice with pulp, and eats pasta if al dente, some raw carrots and broccoli, pizza, all fruit except bananas, and salad greens with ranch dressing and cheese. And bread. Loves bread. We've come to the realization she has real sensory issues. We've tried every tactic - forcing eating resulted in vomiting. Restrict until she ate it resulted in weight loss.... I understand.
WDW trips can be hard, we do a lot of buffets, she eats lots of bread and modified salads and fruit, and we do the plate switch if all else fails. We do let her look over the all ears menus ahead of time, and she can get an idea of what she'll order or try. She's nervous about Biergarten -first because the name makes her think we are taking her to a bar, and secondly because the pretzel bread is just about the only thing that appeals to her. We'll look when we get there and hope she can find a few other things. I have the feeling that she'll be eating something else later. Our approach has been, lately, we understand. We're not forcing. Here's what's available, see what you can do with it, fill up on what you like and water! Sort of passive-aggressive I know, but she's going to have to learn how to make her own accomodations!
Hang in there. Wish I could say it gets easier, it just becomes more routine and easier to accept!