The cruise lines are a lot more particular with the ages of their guests than the party hardy hotels in Cancun. Spring break has made Cancun famous and they are not about to disourage their guests by requiring "age limits". However, no matter where you vacation during spring break, you are bound to be surrounded by kids with their parents on most of the ships. If you don't mind that, you should be okay. I have read on this board that the new RCCL ships are very popular with families. If you stay away from the ports in Mexico you probably wont have a problem with the kiddy-peddlers.