Another option is to do some research before you go about the islands you will be visiting and decide what you want to see/do. There are always lots of local people with taxis/people carriers at each port who will be only too pleased to take you where you want to go or give you a tour of the island at a fraction of the cost of the ship's tours. We are back in the Caribbean in March - can't wait. I am sure you will love it - enjoy your cruise.
Many people may thinking that I'm mad giving you this piece of advice (and maybe yourself!) but if the child in you is screaming out try river tubing in Grenada. When I went on it it appealed to people of all ages (the youngest being 12 and the oldest I think about 60+).
We also went on a snorkelling and shipwreck tour in Barbados. We swam with lots of wild turtles who were being fed by the guides. Go on the land and sea tour in St. Lucia. You will sail on a catamaran to the pitons and travel by mini-bus to the drive-through volcano, the only one in the world apparently. Then you will visit a plantation and have lunch before driving through the island back to the ship. The weirdest sight we saw was a banana plantation for Sainsburys! In Aruba we did the submarine tour (visited a WWII wreck), Bonaire is excellent for snorkelling or you could go on a sight-seeing tour to see the flamingos. There is so much to do that some excursions we couldn't go on because they were full or we had something else booked. Have you received your excursions book yet? If not, go on www.princess.com. You can actually view and book excursions on the website. Hope this helps. Enjoy your cruise - we have another 15 months before we go again!