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There is a lot to do on the Freedom class of ships. The basketball court is full-size and they also do volleyball there and some other games. You also have the Flowrider boogie-board/surfing venue. They have the Living Room 'kicked back' area for teens, and as you mentioned the 'Fuel' disco, which is for teens only.
The Freedom has an outstanding fitness center which your son will like.
The Freedom is a great ship for teens. We were on the inaugural voyage of Freedom and it is one of our favorite ships.