You have to call Disney Dining, get through to the chef in charge of allergies, leave a brief and to the point message stating what information you need, along with name and phone number. Once you do that, they should call you back in a day or two.
As long as you're going places where they actually MAKE the food, you should be OK. There's a gluten free list available at City Hall. They don't send it out ahead of time b/c things can change.
We have to avoid colors, corn syrup, corn syrup solids, and HFCS. Good bye most of the packaged food!!! Including Dole Whips and most of their ice creams. So we go to the Haagen Dasz place in DTD; they have an ingredient list right behind the counter. As I'm sure you know, the simpler = the better with them!
We bring in most snack foods. DS has powdered sugar on his waffles and pancakes b/c the syrup they have at DLR isn't maple syrup at all. It's *possible* that the syrup at Storytellers is real, but DS is so used to powdered sugar (which, if it were an allover corn problem he coudln't use, b/c they use cornstarch to make powdered sugar more easily pourable if that makes sense) that he didn't care.
Counter service places also have binders with ingredient lists in them. I highly recommend going at NON "rush hour" eating times unless you're comfy with stepping aside to read the ingredients while others hurry to get their food.
They do allow you to bring in your own food, so we bring in, say, peanut butter and jelly sandwiches with safe bread, PB, and J. Uncrustables are filled with nonsense so DS can't have them. DS has also gotten used to mustard on things like fries b/c of mainstream ketchup's ingredients.
Anyway, I'm not telling you things for YOUR situation, but what WE do to work around things.
We haven't had a problem yet. I've even gotten a platter of veggie sausages from Storyteller's (I only wanted 3 patties, he brought a platter, yikes!), that's how accomodating they *can* be.
Have fun!