Wendy,
When my son was diagnosed at age 11, his GI put him on a low residue diet. Ben is also a picky eater, and was actually happy because now I couldn't force him to eat vegetables! I still have a copy of the diet, so I will give you some highlights, but I'm sure you can find this information online. Generally safe foods are white toast, low fiber cereals such as rice krispies, rice chex, kix (without milk), oatmeal (without milk), bagels, english muffins, white rice, pasta without spaghetti sauce, pretzels, animal crackers, tuna packed in water, chicken, eggs, potato, canned fruit (except those containing grapes, pineapple, fruit cocktail). When my son is flaring he eats mainly chicken and rice and I have him drink lactaid instead of milk and also the lactose free ice cream, and no fresh fruit. When he is doing better he can tolerate milk and milk products and eat fruits like bananas, pears, and cantelope, although he does peel the skin off the pears. Citrus fruits upset his stomach. It is a lot of trial and error. We found that Ben cannot eat corn, even in tortilla chips. Also some brands of spaghetti sauce bothered him while others were fine.
Hope your son feels better soon.
Take care,
Nancy (son Ben, 15, CD; Remicade, Milk Thistle, Probiotic, Multi-vitamin)