RCI Is the best for kids programs! i'm 14 and was on the explorer recently, it was by far the best cruise i have been on! if you want a smaller ship, (slightly!) and for your kids to have a blast, try the Princess grand class ships or the new Caribbean Princess.
I have not tried a celebrity teen program and am going next april but am also wondering what the program offers. I cant answer for the millenium class ships but i've heard that teens wil have alot of fun on them too. They arent as big and will still provide as much fun to your teens as to the whole family!
Have a great cruise!
I am currently 19 years old and I have cruised at the ages of 8, 11, 12, 14, 17 and in 23 more days will cruise at the age of 19 I also have a sister that is 2 years younger so she has cruised at the ages of 6, 9, 10, 12, 15 and soon 17. Our first cruise was on Royal Carribbean, and all of the other ones (including the one we are about to go on) have been on Celebrity. Although Royal Carribbean wasn't particularly bad, Celebrity in our opinion is much better. There are people from all over the country that I met via the kid's programs on our last cruise that I continue to keep in touch with, and I know my sister still talks to people she met on the ship too, and that was 3 years ago! If you are looking for a midsized ship, then I would advise you to stay away from Royal Carribbean. That was our biggest complaint about that cruise- the ship was so big that you never really felt like you knew where you were going. On the Celebrity ships you really know your way around after a day or two, but at the same time you certainly don't feel as though you are cramped or that the ship is too small. Personally, I would strongly reccommend Celebrity. I hope I helped and enjoy your cruise!
As some one in the travel industry who deals with lots of families doing cruises. I would have to reccomend Royal Caribbean Cruise Lines (RCCL) the parent Company of Celebrity Cruises for teenagers.
There is a great mix of things for them to do and Celbrity also has a Teen Club, however it is RCCL that has taken the time, money and energy to specialize in this area. All the families that I have sent to date have enjoyed both cruise lines but still rank RCCL as the best.
Feel free to contact me directly at my email and I would be more than willing to assit you on this.