Princess Cays is a beach day, no excursions really except for a glass-bottom boat tour. Otherwise you can rent a variety of water sports equipment and relax on the beach. Check the list on Princess.com:
Explorer of the Seas October 2013
Caribbean Princess July 2006, May 2010 & November 2012
Monarch of the Seas November 2008
Crown Princess November 2007
Celebrity Zenith November 2005
Enchantment of the Seas August 2004
Princess Cays is a beach, with some shops and Princess will have food there and and servers on the beach so you can get drinks.
There seemed to be plenty of watersports, I did the Banana Boat ride and it was a total blast..got thrown off twice.. I am sure your kids will love it..other than that, mostly chilling and swimming, etc.
It was much nicer than I expected, so I hope you enjoy it..
1999-Carnival Sensation, 2000- Inspiration, 2001- Destiny 2002-Celebrity Galaxy, 2003-Constellation, 2004-Constellation 2005-RCCL-Adventure of Seas, 2006-Constellation
2007-RCCL-Seranade&Explorer of Seas
We've been to Princess Cays a couple of times and didn't do any excursions. We rented snorkeling equipment. My 14 year old did the banana boat. Princess has lots of activities planned during the day. There's a fenced off area in the back of the island that has all "locals" selling arts and crafts etc. They're cheaper than the shops on the island and the people are always great to talk to.
I got TOASTED at Princess Cays. Even wearing the super SPF 60 sunblock, make sure you re-apply it often, and PLEASE DEAR GOD pack some After-Burn with Lidocane because for some stupid reason, they do not have that on board in the shops. I rented their snorkel equipment and had a great time in the water, but our last cruise we bought snorkel equipment of our own and packed it with us. It was cheaper than renting, and I didn't feel weird about putting something in my mouth that thousands of other people had already used. Oh, yes, and get an underwater camera for each kid - CVS has them around here - much cheaper than buying on board - your kids will love it!
There is plenty to do there and you can rent equipment there like for kids and adults to play with. You will have a large buffet lunch there and visit a couple of stores. You can walk around and they have water there for you so you don't have to BUY their bottled water they will try to sell you on the ship at each port.
Nice swimming and snorkeling near where the food will be served.
Get to shore early and get some chairs with SHADE as they go first.