Mumsy,
My suggestion is to plan your own days, and your own excursions of sorts.
Grand Cayman has a great company called Captain Marvins
www.captainmarvins.com We took the two hour stingray excursion and had an awsome time. Our group of 19 ranged from Adult down to some 7 year olds and a 3 year old.
We all had a blast. The 3 year old didn't get out of the boat and loved watching the people swiming and seeing the fish in the water. The three 7 year olds didn't get out except at Stingray City and they loved it too. We just alternated being with them so they didn't get uncomfortable. The people at Captain Marvins are wonderful. They really took good care of us and included all of us, even the 3 year old who didn't get off the boat.
At Cozumel we rented a jeep from
WWW.COZUMELINSIDER.COM cost us $45 for the day and we didn't have to walk but a few blocks from the ship to pick it up. Wasn't fancy, but clean and it ran well. We drove about 15 minutes to a place called Mr. Sancho's Beach.
WWW.MRSANCHOS.COM Free entrance, very clean beach. Lots of little shops, great food... great fun. We left when we were ready and did a little shopping before heading back to turn in the jeep and get back on the ship.
Key West was a waste of time as far as we were concerned. Nothing much to do there and it seemed dirty and hot!
So... that's my 2 cents i'm sharing with you today. Feel free to email me if you have more questions. I can send you a link to my pics if you'd like. Just get me your email address...
Dios te Bendiga!
Jodie