i really feel for you - i had a love-sick 18-yo DS at OKW 3 yrs ago - he refused to go anywhere with the rest of us; just wanted to hang around OKW and the pool - making himself and us miserable. We normally bring a friend with us but that was a time when no one could make it. I bet once he gets there he'll feel better - he's still a kid.
Here's a thought - check out this thread about Secrets and Little Known Facts about Disney:
http://www.disboards.com/showthread.php?t=2059651 There are tons of secrets that a teenager like him might really get in to looking for while he's in the parks. I know DS loves this kind of stuff.
good luck and have a great vacation!