I also looked at David Klein's diet, but I was so sick at the time, I knew I couldn't handle the roughage of raw food, which can be very irritating to an inflamed gut, and I wasn't willing to juice everything.
Kudos to you for looking for alternative/supportive therapies for your son. I'd highly recommend a couple of books for both you and him to explore: Optimal Digestion and Listen to Your Gut. These are both packed with information on ways to treat UC beyond the usual meds. Optimal Digestion also offers alot of eye-opening information on how a healthy digestive system is supposed to work and the ways we contribute to things going south - diet, antibiotic use, stress, etc.
I have been mostly in remission for several years due to a combination of ASA maintenance drug, clearing the system of bad gut flora, reestablishing good gut flora, dietary changes and lifestyle modifications. It's not easy and it's not quick, in my experience, it's what you have to do to get your life back.