DS will be 15 tomorrow and we were at POP in January. It is a really cool resort for teens. There are several pools and a game room they will enjoy. A great food court with lots of teen choices.
They will enjoy all the parks as there are things for teens in all of them. Thrill rides to shows. Down Town Disney is fun too. Let them help choose some of the resturants. Most teens are not too into Character meals anymore. DS loved Coral Reef, Ohanna's and Le Cellier. Prime Time Cafe and Sci- Fi are great teen choices too. They might like Disney Quest and renting mouse boats if extras are in the budget. I would be ok with the three of them having a little freedom to explore with-in the same park you are in.
DS likes Epcot the most but loves all the parks.