Thank you for the question,
I agree that he may not be getting enough vitamins in his diet. This is a common and difficult problem in children with special needs. It is very important that his shunt is checked routinely by his doctor-- especially during periods of growth. As far as the question of supplements affecting the shunt, I have not heard of this being a problem, but I would clear it with the boy's physician just to be safe.
If possible, I would also suggest a referral to a nutritionist who specializes in children with special needs. Also, if this has not been done already, seeing a developmental specialist would also be a great idea. I hope this helps.