My ds14 is an Asperger's kid and one of the pickiest eaters ever! (smells, textures, looks - so many things bother him about food). His food issues are just one of the reasons why we bought into DVC so we can feed him at "home" before the three of us eat. (We also have a dd10 who will eat almost anything)
If we have dinner reservations at Epcot if we haven't fed him at the resort yet, we often get him a pizza from the place near Test Track (the name of the place escapes me now)
What are some of the foods that your son WILL eat?? Perhaps if we knew that we could direct you to places to feed him before you eat. There are a few places where ds WILL eat (at Le Cellier he eats the bread sticks and the cheese soup - I have NO idea why those work for him..) And because he needs something to keep him occupied, we are awful parents that let him bring his gameboy to dinner to play so we can eat.
I hope that things work out for you! It is easy for others to say that kids should just find something on the menu to eat, but that isn't always a possibility for everyone. You do what you have to do...
Jill