I assume your ports of call are Labadee, Grand Cayman, Cozumel, and Jamaica. In Grand Cayman, I would recommend doing a Stingray City excursion. There are plenty of them offered through the ship, and I would recommend doing it if this is your first cruise as opposed to going independently. This is a great experience, and maybe even a once in a lifetime experience of swimming with sting rays.
In Cozumel, if you're looking for a beach day, I have heard good things about Paradise Beach. Go to the taxi stand once you dock and tell the driver you want to go Paradise Beach. Cabs are plentiful in Cozumel, and they are also probably waiting at Paradise Beach to take you back to the ship when you're ready to leave.
Those are the only recommendations I can offer, as I have not been to the other 2 ports, but probably will maybe early to mid fall, which is when I'm looking at a similar itinerary.
2007 - Majesty of the Seas
2009 - Enchantment of the Seas
2010 - Freedom of the Seas