We have 4 kids ranging from 14 to 20. Since we needed 2 cabins, we needed to watch the dollars but at the same time wanted the kids to have a great time both on the ship and in the ports. We found the Carnival Conquest (carnivals largest ship) out of New Orleans.Ship is 110,000 tons of fun! We booked one balcony and one inside cabin. I went on the internet and booked my own excursions and ended up not only saving money but experienced the time of our lives by fully enjoying each port. Montego Bay was our favorite because we booked with a private tour guide, determined our day of activities, and then went on line at www.cruise-addicts.com
and invited people to join us (two families jumped on it right away) the whole day only cost $20 per person plus food and entry fees. Grand Cayman was captain Marvins and stingrays with beach after.
Cozumel was beach, snorkel, Carlos and Charlies and some shopping. Total cost for the cruise was about 6K for the 6 of us. Many other teens on the ship and all our kids made new friends. Our kids are begging to go again and say it was our greatest vacation. (we've had some great ones). I have compared RCL and Carnival and Carnival always comes in about 15 % less than RCL. I wouldn't pay the extra just for a climbing wall and a skating rink which is a feature on the Voyager class ships of RCL.
If interested, I can give you more info.