I took my family on this cruise. I am a single mom of 4 boys, twins 22, 18, and 13. And we took along one of my son's girlfriends with us as well. We had a pretty good time. The service and staff were almost all very nice. The room was cleaned endlessly and the animal towels were fantastic each evening. I have T-Mobile and had no service (not even roaming) after the first night. So I suggest you have walkie talkies for your children if you don't enjoy searching for them all the time. Also you need your Sail card for everything and it is so convenient if you bring a lanyard with a card holder (for each person) with you to have around your neck instead of taking the card in and out of your pocket all the time. This is especially good for the kids. Also one night at dinner is "formal night" and you need dress clothes. A pair of khakis and a collared shirt will suffice. The restaurant staff doesn't enforce the attire, however.
There are a lot of excessive charges. Bingo is $20 for three cards. This gets expensive when you have children who want to play. And although Carnival charges each person $10 a day for gratuities, when you buy an alcoholic drink they add in a gratuity. Or if you buy a pastry at "Creams", there is a gratuity added. It gets pricey after awhile.
St. John is a bust. A total waste of time. We didn't take the Bus Tour as a friend of mine who had been on the cruise said it was a waste of time.
We walked around a bit. There is a really good coffee place in the mall. (And you'll need it as Carnival's coffee tastes like dirt). The New Brunswick Museum is a waste. Photograpy is prohibited. The kids were bored. The ship is pretty empty while the boat is docked. There are few if any activities scheduled while in port, and the casino and all the shops are also closed.
Getting off the ship in New York would have been an absolute disaster if I hadn't thought "outside the box." Carnival takes your luggage between 9p and 12a the last night of your stay so they can have it ready to unload upon docking. You have to be out of your room by 8:30 and Zone by Zone you get off the ship. We were Zone 16..scheduled to get off the ship at 9:15 to 9:30. I had my transportation set up to pick us up at 10am. Well at 9:15 am they were still on Zone 1. So, I just went in line and got off the ship with everyone else. I grabbed a porter...gave him some cash and he helped us get our bags, get through customs and get to Pier 90 by 9:45. We were home by 11am.
Carnival needs to get a better grasp on the disembarking process. I would have been on the ship until 12 or later had I not just decided to get on line, despite being Zone 16. I don't know if I would have done this if I wasn't paying $200 for the car service.
One more tidbit. Keep an eye on the charges to your card. You can go to Guest Service at any time and get a printout. With four kids it added up quick. I had over a thousand dollars of charges for four days!!!