We are going on our 6th disney cruise tomarrow and we have done lots of great stuff. Since you are teens, be sure and check out (The Stack). It's a teens only club. No adults allowed. I am a little too old for that, however my grandaughter is a teen and has been. I know they do teen only excursions at most of the ports, you must sign up when you sign up for the other excursions with your family, they have music in the stack, pizza parties and movies, dancing. Games and they use to have an espresso bar too, I don't know if they still have that or not. I know you can eat with the teens if you don't want to eat in the dining rooms with everyone else too. Of course your family may want you with them so you can share all your great experiences.
It may sound kind of corny, but if you like the animal towels they will leave in your room each evening, they do have a short presentation on how to make some of them. People of all ages attend that. It's really fun to do. They also have studio C which is a family type night club at night with dancing, Karoake, and they have games like "Walk the Plank" or "Who wants to be a mouseketeer?" Our family has had a lot of fun with that too. The Mickey 200 is a fun race for families too. You have to arrive a little early as only 16 teams can compete. You have about 10 minutes to make a race car from a potatoe, a carrot, 2 sets of wheels and about 4 toothpicks. One tip is they usually give a medal for the design of the car before the race too. We won that because we cut a mickey head from one end of the carrot and stuck in in the drivers seat with a toothpick. You can practice at home with a potatoe and carrot too. I don't know about the excursions on the western cruise as we are doing it for the first time in December with all our family. But on Castaway cay there is lots to do. The main beach gets crowded fast, so grab a chair early. The glass bottom boat ride is great if your into colorful fish or have younger kids, it's a easy excursion to do. For more of a thrill I highly recommend the Banana boat ride. 8 of you can go on one boat. You have to be able to swim and be at least 7 years old. My husband loved the Parasailing, but it's spendy. The grouper game room is fun, they have shuffleboard, hoops to shoot, chip it golf, a sand box, a very large chess and checkers set, and a pool table. No extra charge. You use to be able to make a kite on board then fly it on castaway cay too. We rented bikes once, but the island is small enough we could walk around it just as easily as riding.
Eating in the restaurants is very entertaining, not like a regular restaurant. Pirates night has lots of surprizes at dinner, but i wont say what. Animator Palate is great to watch the colors change throughout the night too. Of course the musicals in the evenings are great and the comedians and jugglers are funny as well as entertaining. I heard they have some new show that is a flop on the wonder . It was just to fill in until the new cinderella show starts later this month.
If you would like to make some new teen friends before you cruise, go to Daves tribute cruise site and fill out a new post there and you'll hear from lots of people. That site is the most popular with disney cruisers, just title it something like, any teens going on then the date of your cruise. You'll get a response I'm sure. We do that for all our cruises. Most of the teens do private messaging there so we old folks don't know what they are up to. HA! HA! hope I have helped you some, have a magical cruise.