I have never cruised before but I would highly recommend the carnival victory ship. Although it holds a lot of passengers it never felt full or over crowded anywhere. Here is plenty to eat and food all round. Alcohol is quite pricy (for a Yorkshire girl) however you need to have some money set aside for them before you go! All the cocktails were fantastic (and I had them all) as well as the food. The ports you visit are breath taking. At St Martin I recommend you go to the airport beach, it is an eye opener (not for the faint hearted). Don't pay for a taxi or tour just go two streets back and little busses come along all the time with the name of the place and it is only 2 dollars each way!
The only negative I have is if you board at Barbados you have to get off the ship and go through immigration at San Juan and it is a long process getting off and on so take a book or something to entertain you and get their first of last.
I recommend a room with a balcony however all the rooms were lovely. Soft bed, lovely couch, plenty of room to store clothes. There are lots of photographers around the ship, don't get in the big queues, just wait a little and then go for it!
All the staff are really friendly and know you by name by the end of your trip and if you are a couple then I recommend the over 21 area found at the top of the ship. . It has a bar, hammocks and hot tubs! We spent most of our time there! There are clubs for children up to 17 years so I hardly saw any the whole week.
Over all, great fun, plenty going on and if you are British, much of the night club is American R&B music so hit the casino and comedy club (get there early it fills up) and other music going on in the main areas. There are plenty of good singers and music. Shopping is St Lucia is good as well. Get souvenirs there!