You may have booked by now....but we took our kids on RCCL Voyager of the Seas and they had the time of their lives. The sports deck was fabulous, with in line skating, rock climbing, a full basketball court and excellent mini-golf. We're probably going on Carnival Triumph with them this summer, only b/c of the dates and itinerary and I'm hoping they won't be disappointed! My husband and I have sailed on RCCL Grandeur, and would not take the kids on that one due to the relatively small size.
Have fun, Jozy