I went on the exact same cruise !!
Do some cute shopping and stuff in cozumel !! Then go to Chakkanub National Park !! Its very coool .. lots of marine life sort of enlosed by rock formations .. its gorgeous and not a national park at all .. theres a bar hmm gee i wonder !! Its very fun anda great place to go for anyone !!
In cayman do some kind of snorkel tour/stinray city excursion ! I did one that did both it was great !! That was my favorite place !!
In Ochos Rios definately do a dunn river falls excursion .. do it earli-er in the morning ! Make sure to stop by jimmy buffet's margaritaville .. dont venture to far off .. Its not the nicest of places !
Have Fun !!