We have cruised both Carnival and Royal Caribbean, in that order. We made the mistake of going on Carnival in June, 1995. . .right after high school and college graduations and the end of the school year. We were overrun by kids of all ages.
Not that I dislike kids (I have my own.), but I want to relax on vacaton!
We cruised RCCI last August 28, and there were very few kids on board. I think the time of year had a lot to do with it (School was starting that week most places.) as did the itinerary (southern Caribbean). I was never more relaxed on any vacaton.
We are doing Carnival again this year, but in September figuring most kids will be in school.
Hope you have fun!!