We are taking the same cruise in December.
Cayman - I hear the sting ray tour is a must. We booked on our own through Nativeway watersports - $25 per person small groups.
Cozumel - We are opting for snorkeling and then we will go to the beach on our own probablly to playa San francisco. You have to be careful what beach you go to - some have sand that goes right into the water others are better for shore snorkelling and have a rocky entracne. The last time we were there we went to Chankaab Park - beautiful but had a rocky entrance. The dolphin encounter was nice, but do not need to do it again. Also very crowded. We also went to one of the beach clubs - somewhat tacky. Won't do that again.
Roatan - we are going to do the Tanyana beach break package. I have heard great things.Beautiful beach, nice drive, etc.
Belize - I think we will go to Caye Caukler - suppose to have lovely beaches - 40 minute boat ride from port. No cars on island - very relaxing and great for children.