Kat, although all 3 cruise lines have good children's programs, I think you will find the passengers a bit older on average on Princess. RCCL and Carnival are both great for families - the "nonstop party atmosphere" is something you're more likely to find on the 3-night weekend cruises, and Carnival is trying to discourage the party-hearty image. I have sailed on all 3 lines (at different times of year). If you are doing southern Caribbean, Carnival and RCCL's Voyager class would both be good bets for a family group. Please see a travel agent - they may know how to get you a better rate for a group of people.