We did the western Caribbean, visiting Labadee, Falmouth, and Cozumel.
The big thing to do at Labadee is the zip line. The roller coaster is also popular. Labadee has really turned into a huge private resort, made better by the pier.
Falmouth was a disappointment to me because I wanted to see the port area which is supposed to be a British colonial styled place. Yes, it is all fake but I wanted to see it so I could write about it. Sadly it is not close to being finished. I'd say 50% or so. Falmouth is really just a jumping off point to tours that one can get when docked in Ocho Rios or Montego Bay. Teens would likely be bored with the plantation tours and such. It really means doing the familiar tours like the Dunn's River Falls or Martha Brae rafting.
Cozumel has always been my favorite place in the western Caribbean, and I guess it still is although this time I got annoyed by the store hawkers downtown and had a 'moment' with an uppity Mexican security person when I was returning to the ship. Thus I am a bit jaded about this visit. The port areas and main drag are so phony and commercialized now days that it has destroyed the charm Cozumel used to have.
Just get a cab and go a beach or day resort. Don't buy a ship's tour for Cozumel.