Having a child who is on a specific diet is really trying sometimes. I am writing a cook book for children with enterocolitis and there are so many foods that I have been making interesting for her. I have very simple recipies that taste good and it seems to work. I add corn to her four bean chili, and things like that. She ate all the mushrooms out of the brussels sprouts and she refuses to eat pasta without mushrooms. She likes peas in "Bister" a marinara sauce my mom taught me to make. We will add canned vegetables to salads.
There are a lot of cookbooks online for kids foods. There are some really neat tips. If you figure out a weekly menu and then go shopping it really helps to make sure that there are some vegetables on hand.
I hope this helps.