My sister is gluten free, and was dairy free as well for a LONG time. DH and I are vegetarian so we TOTALLY get the food allergy thing. Honestly, I would stay away from Il Mulino. As much as I LOVE that place, there is WAY too much gluten in that kitchen and cross-contamination would be a big issue. They didn't quite understand the vegetarian thing and wanted to serve us fish, gave us an anti-pasto tray with meat on it, offered me soup made with meat stock... you get the idea.
If he likes fruit, you can get that most any place. I don't know the email off hand, but if you go on Disney's website you want to look for Special Diets around the Dining section of the site. They won't have the S/D restaurants on there but they will have a list of allergy free options at the different WDW restaurants. This will be a good place to start. For example, you can get GF vegan mickey waffles by special request at some of the restaurants. I think they're made with Bob's Red Mill flour.... rice flour maybe? I don't remember. But start there and don't hesitate to call the S/D and ask to talk to a dining manager.