V.T.
My sister took her kids that were 4 and 5 on a Carnival cruise and signed them up for the Carnival Camp Kids (or something like that). Her kids loved it. They had games and activities to keep the kids occupied all day, and I think as late as 10 pm. The cruise lines also have babysitters available to come to your room. Carnival, I believe, is the least expensive out there. And depending on when you go, you can spend less than $400 a person. You have to figure that anywhere you go, you will need 2 hotel rooms, at about $100 a night per room, you really are saving money by going on a cruise, because the $400 includes room, food and activities. As for the 21 year old, all cruise lines will probably be the same, since at 21 they can take part in all activities offered on board. I don't believe Camp Kids cost anything additional, but I haven't found a cruise line yet, that doesn't charge full fare for a kid.