Try posting this on the teen board also, you might get some good suggestions.
A segway tour is a great idea (DS17 has always wanterd to do that), I'd also suggest the meal with an imagineer which some friends have said they enjoyed. (if you think he'd like it, they said there DS19 did). If he's into food take him to V&As, you could also do something at the Wide World of Sports (not sure what the age is to drive a race car, DH did it a while back).