Sounds like you don't know him very well. As Todd said, give him a call to talk about it. You might find that he's looking forward to eating what he shouldn't or can't at home. Like that commercial that's on now that has the line,, "Don't tell Mom!". If it was me, I'd eat your stuff and go light on anything I'm not suppose to have, after all,, he may want to please the rest of the group being the new guy. If that's not the case then have your son buy his food.

We don't generally have anything made out of cows milk or wheat products which rules out pasta, bread, butter, cheese and all kinds of good stuff but when we were sailing we had pizza. It was really good.