My son is 19, but has been going to WDW and staying onsite since age 15. His favorite hands down is the Boardwalk area. Always something going on, an easy walk into Epcot or MGM and also easy to get to MK (walk thru Epcot, catch the monorail and go to MK).
As the previous poster said, if you have been before and they are familiar, it is a pretty good place for them to go off alone. Yeah, it's a family vacation, but it does seem like teens almost NEED some time off by themselves. If yours are not familiar with the parks, you might try splitting up for an hour or two and then meeting back at a designated spot. Or, just letting them explore the resort and Boardwalk area. If you pick that area, there is a choice of YC/BC, Boardwalk or the Swan/Dolphin. If you're particular about your rooms and you have 5, you might look into a 2 bdrm at Boardwalk or YC/BC. They are part of DVC and it's just like having your own apartment at WDW