My son and I did this same cruise last Feb. It was SOOOOO MUCH FUN!!!
In Labadee we did the Dragon tail coaster unlimited rides. You only have to pay for the "car" that two people can ride in. So basically we bought one unlimited wrist band for the two of us.
We also went on the Zipline and it was AWESOME!!!

The view alone was worth the price. It took about 2 minutes to go down and not scary at all. You also go on a shorter zipline as a test run before the main one.
We relaxed on the beach and did a little shopping. The shopping 'alley' is a bit much as they hound you CONSTANTLY however the little market building is great. No pressure and very neat stuff. The ship is docked right there so you can go off and on the ship several times if needed.
In Falmouth, it is just a shopping port. Anything worth doing is about an hour bus ride away. We chose the Dolphin Experience and Dunn's River Falls activity.
THe bus ride is fun and our tour guide was a hoot! We stopped at Dunn's river first where you climb a waterfall. Very cool! Then we drove a quick bit to the Dolphin cove where we got to have some time with the dolphins. There were about 8 of us in the pool with "Betty" for about half hour. She pulled us on her belly, swam around us, did some tricks and then we got to hug and get a kiss from her for the camera. There are a few different levels of the Dolphin time, so the more you need to look into that depending on how much you would want.
By the time you are done and back, the ship is almost ready to be boarded.
The ship is amazing and there is so much to do!
I can post a link to my trip blog and also to the Cruise Critics boards. You can learn as much about cruising on that site as you can about Disney on this site.
Here is the link to our trip
http://boards.cruisecritic.com/showthread.php?t=1591461
Here is a link to the RCC boards
http://boards.cruisecritic.com/forumdisplay.php?f=83
Have FUN!!