We have done two Disney Cruises so far. Started with a 3 day (first cruise ever and didn't want to be stuck too long in case we didn't like it) and then a 7 day. Our son was 7 for the first one and 8 for the second. The kids will not be bored or disappointed. The kids area is fantastic and they get freedom from the adults (or you get freedom from them, however you want to present it). The ship (both the Wonder and the Magic) were spectacularly clean and we felt like the cast (staff) was always there to serve us and make sure we got everything we could want. I plan to do it again as soon as I can.
On the 7 day we did Tortola, St. Thomas, and Castaway Cay. We snorkeled in all locations and it was great. Our original plan was to dive, but that would have meant our son would have missed out on some of the experiences. As it turned out, one of the dive sites was where we snorkeled so we didn't miss anything. The crew of Castaway Girl (who our snorkel trip was with) was excellent as well. I would book another shore excursion with them as well.
We brought all our own snorkel gear so we didn't have to rent it and that was not a problem anywhere we went. I guess I just prefer my own stuff.
I do not work for Disney and no one in my family works for Disney.
One thing I will say, if they say the boat leaves at 6:00 PM so be on before then, they are not kidding. You can bet that at 6:05 PM there is a significant gap between the doc and the boat. There were people who were running to make the boat because they were careless.
I can't address the previous comment about not doing the Disney Cruise without the kids because I have not been on a different cruise line yet. I don't know that I would call myself a Disney fanatic, but I have high expectations of Disney and so far they have delivered and then some so for me, I would do it with out the kids.
Keep asking around and ask for some literature (and DVD) from them and take a look. The DVD does a pretty good job of explaining and showing what is available on the ship. When my son first watched it (when booking our 3 day), he turned around to us and said, "I won't have to see you for three days!" Yep, with the kids programs he would chose what he wanted attend and he never once was "ready to leave" the kids area on either of the cruises.
We booked through
Small World Vacations - Authorized Disney Vacation Planner Small World Vacations Small World Vacations, Inc. - Walt Disney World Vacation, Disneyland Packages, Disney Cruise Line Vacations and Adventures by Disney!
MouseSavers.com - Disney Discount Source - Disney World Discounts, Disneyland Discounts, Disney Cruise Discounts also has a wealth of information on anything Disney and it on this site that my wife found the travel agent that we used.