We used Moby Dick Tours and did Sting Ray City on our first cruise to Grand Cayman and it was awesome. The boat had maybe a third of people compared to the cruise ship boat excursion. Cost half as much and included snorkeling over a nearby reef. Plus the crew was wonderful. Last time we did the turtle farm which was good for the little ones (under 5). If we ever go back and my kids are the same age as yours we will do sting ray city again it’s that awesome.