The teens can take advantage of the flowrider on the first day (embarkation day) since the lines are pretty short. Take swimsuits with your carryons and not luggage this way the kids will be able to change into swimsuits and enjoy the flowrider just in case if the luggage is not in the cabin in time.
70's nite in the promenade is a blast! There is a evening flowrider deck party one nite for the kids also a disco nite for the kids where the kids take over the disco (no adults allowed)
Have your teens go to Fuel the first day this is where they will meet other teens.
And once teens experience a Freedom class ship it is difficult to get them to go on another cruiseline.