One of the most fun things my 17 year old enjoyed was getting the sea raycers. Those are the small 2 person boats you can rent from several resorts. Its not only fun to drive your own little boat, but it is interesting to see the resorts and MK from a different perspective. Do this before 2pm as the afternoon storms will shut the rentals down. All of the cast members at the EPCOT world showcase are from the country they work, and many are 18-22 years old. Its a lot of fun to talk to them about their country. If you've never done the water parks, they are a blast for teens. Search for hidden Mickeys or other secrets of the parks. Then there is all the specialty food items - zebra domes, dole whips, kona coffee..... Oh - the Japan Pavillon in EPCOT has a Pick a Perl experience that I hear is fun. But I love the shopping there. As a joke, I always buy a few packs of the freeze dried fiddler crabs to bring back as gifts for people. They smell horrible and it takes weeks to get the taste out of your mouth. Much worse than Beverly at Club Cool.