We did a Carnival cruise out of Tampa. There were kids on the cruise and they seemed to have a good time. There were camps for the various ages and the activities looked good. Carnival gives parents a phone type thing so that they can be contacted anytime during the cruise if needed. Maybe other lines do this also.

You might want to check out www.cruisecritic.com message boards since they cover all the lines and have forums about kids. Under the boards they have a specialty section and a sub forum of family cruising. This covers cruising with kids and lots of posts.