Carnival is known as the Fun Ship Cruise. I have sailed on them 2 times, and found that you can't beat it for the price. On the newer ships, the lowest priced cabins are very large (for a state room), nice sized bathrooms, great cabin service. Really good food, I thought it was much better than
DCL. The age range used to be the 20s, but now on longer itineraries like the one you are considering, there will be more people of all ages. They may not have a Camp Carnival at that time of year, so you may not have a lot of kids. I say go for it, cruising is probably one of, if not the best vacation value going. Great food, entertainment, no unpacking after the first time, the ports are nice, usually there are good shore tours available. I have cruised 13 times, I love it.
The downside of cruising can be: if you don't want to eat a specific time and with people you don't know, it could be a problem, although there is room service and less formal dining options available. THere are tons of activities, but if you are not one who wants to play pool games, or bingo, horseracing, etc, it could be less than fun. My husband hates cruising, he says it's a cattle call for meals and shows, and he isn't into all of it. He has cruised 3 times and will never do it again. I go with out him.