Reserve the Dolphin swim ahead of time to make sure you can go. (get's pretty crowded and you are there on a Friday). In Cozumel, as soon as you get off the ship,walk straight to the Taxi stand which is behind all the shops. Pay $10 total (not per person) to Chankanaab. Once at Chankanaab, walk right to the beach and head south until just south of the raft. Set up your beach stuff there. Clean restrooms,bar, food etc.. right behind you. Snorkel in the water along the shore until time for your dolphin swim.
In Grand Cayman, book earliest and shortest tour with Captain Marvins. Take earliest tenders to shore. Walk 3 blocks to Captain Marvins storefront. While waiting for van, you can do some quick shopping right there. They pick you up and drive you to boat. When snorkeling and at Stingray city, try to have you and kids do crazy things in the water. Hold hands, wave, hold Stingrays, have them put them on your heads etc.. The video photograper with Cap. Marvins will catch this all on tape. You can then purchase that video(put to calypso music) as a souvenier. Once off Cap Marvins boat, have driver drop you off at Holiday Inn Beach. Holiday Inn is free, and they have a great open air restaurant for lunch! After lunch, lay around on 7-mile beach (beautiful!). Finally, walk to Taxi stand and go back to dock.
In Jamaica, book Carolyn Barrett but once you have an itinerary with Carolyn, list your itinerary on these message boards and invite others (especially with kids your kids ages )to join you and split Carolyn's cost. You'll be amazed at how quick people will join you because many of them are apprehensive about doing it themselves but will join if someone else sets it all up. After your river experience, ask Carolyn to take you to the local jerk chicken stand (great food but I would never have driven in there myself!)
also, she knows a small craft fair to get good deals on Jamaican crafts with no one to hassle you.