I have been on the Fantasy a twice. It is an older but nicely kept up ship. Having just had a refurbishment, everything will appear brand new.
I have taken cruises with my friends and they are alot of fun. You have someone to talk about your cruise before you go, like what you are going to do where and stuff. When you are onboard you always have someone to hangout with and when the cruise is over you can still talk about the good time you had. When I went we usually have our own room, which is cool because we can come and go when we want to, and not have to have a parent watching us. (On one I think I saw my friends parents like 5 times the whole cruise.)
The food in the dining room is really good (in my opinion) on Carnival. Its nothing gormet or gross, but tastes really good. Carnival has good pizza, and you can get it 24/7. I dont think Carnival has started using crufews yet, but I bet its on the way! I wouldent let if keep you from booking a cruise, after all, crufews are extreamly hard to enforce with teens these days.
All in all, the cruise is a really good idea. I would say its worth your parents money because when I went with my friends I had to pay my money and had an awesome time. Go for it!
Here are some pictures of the newly updated inside...
The Grand Atrium
Source: Cruise News Daily
Check out www.carnival.com
for 360 tours.