We did the Western Caribbean on the Valor in April and loved it! We ended up not doing an excursion in Belize, just walked around and shopped, but I regret it. Our friend wasn't feeling great so we decided to wait to have our beach day in Costa Maya (which by the way was cancelled due to weather). Anyway the water in Belize was gorgeous! My friends husband ended up being the only one to do an excursion there and he had a blast. Don't remember which one but he booked it through the ship and a catamaran picked him up right from the ship...you have tender in in Belize.
In Roatan we did a snorkeling excursion booked through the ship. Again, I don't remember which one...sorry..., but I can tell you that in Roatan there are lots of sand fleas so I recommend using a waterpoof bug spray! The bites don't hurt but are really red and ugly. I wasn't bitten because I sprayed that stuff all over but you could see where my husband missed because he was covered with bites in those spots! The snorkeling was decent in Roatan. I've heard they have great spots for snorkeling there but I don't think we hit the right spot because we didn't see a whole lot, but still pretty nonetheless.
I hope you get a chance to do the Stingray City tour in Grand Cayman. What an awesome experience! Although I don't know how much tourism has gone down there because of the Steve Irwin death recently. It really was one of the best things I've done on a cruise!
I hope you and your family have a wonderful time on the Valor!!!