Last year we had a right merry-go round trying to ascertain what special dietary requirements were available in DLP. They did some special meals for gluten free and other intolerances which are limited and to be frank looked gross (we were shown the prepacked meal).
In fact, things were far better than we expected once we arrived. At Plaza Gardens & the restaurant des stars, the chef was able to cook meats and fish without sauces when asked and the service was very good. Inventions bent over backwards to help. Microwaves are available in the plaza gardens and restaurant des stars if you take you own pre-packaged microwaveable items. I doubt that the fast food restaurants could cater for anything bespoke but at least there are good options available in other restaurants