Hi Tracy,
The Walt Disney World Parks and Resorts is a great place to visit if you have any type of dietary needs. My daughter has a shellfish allergy and the chef's at Disney make her feel like a rock star even when dining at the clam bake at Cape May Cafe.
You can absolutely bring food into the parks as well as request a refrigerator at your resort. In addition, when making your Advance Dining Reservations (ADRs), make sure you note both items on your reservations so the chef's can prepare meals for your son.
Disney has come a long way with providing additional food items to accommodate the needs of its guests. For example, Disney's Animal Kingdom has added a list of
quick snacks for its guests who need extra pixie dust. You will also find similar items in the other parks. Also, if you are at a quick service restaurant, ask the cast member if they have gluten-free items. Often they are not listed on the small menu boards but are available.
Some of the best places to find a variety of snacks are
Sunshine Seasons in the Land pavilion at Epcot. This spot always has lots of variety. I would grab a few items here and go on my way. The countries at World Showcase also have great options because they replicate their traditional items which are not necessarily wheat based.
I recommend you email the cast at Special Diets who may have a more extensive list. Their email is special.diets@disneyworld.com.
Wishing you a magical day!
Beth