Is he into thrill rides? If so, you may be able to help him get pumped about rides like ToT, Rockin Roller Coaster, and Space Mountain. He's going to see a LOT of teens while he is there on school trips and with their families, so hopefully that will make him feel better! I went three years in a row when I was around his age and I do remember the first time feeling like I might feels left out or awkward, but one of the best things about Disney is that it can make everyone feel included! Just remember when making a plan for the day to sprinkle in things that are just for him- like thrill rides and cool places to eat. He may enjoy Disney springs or the mini golf courses as well. Maybe Disney Quest if it's still open when you go? if he's into sports, you could spend some time at ESPN zone or eat at Sci Fi or Yak & Yeti is he likes Asian cuisine. Make sure to work in all of the coasters and thrill rides, even if your younger ones don't want to ride them, because he will probably love them! Like the above poster said, maybe let him help with the planning and choose a few places himself. Have a great time, and tell him not to worry- if you look in any direction at Disney you'll see teens EVERYWHERE.