Any of the table service restaurants have an available gluten free selections menu. You have to ask for it. There are a few items at some of the counter service locations. The customer service desk also has a full list at the front of the park.
You'll have to enquire on the spot
You can go to guest relations and ask for the menus with specific gluten free foods.
Ask at any service desk. Also, if you have the mydisneyexperience app, it may display the gluten free menus
The buffet might be best but you really need to speak to someone in Disney for a definite answer.
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