Hi David, and welcome to cruise-chat.
New Years cruises are different than a typical cruise. It is much like the group one would find on a summer cruise - meaning you will find seniors, kids, teens, every group really. This is because so many people are off from work and school during this time.
New Years cruises will have more than the usual amount of partying. Carnival makes a big deal out of the New Year's Eve celebration. But it doesn't get out of control. We went on the Carnival Legend for New Years a couple years ago and brought our then 10 year old son. All was fine and the ship had a fairly large number of young families (young defined as 30 to 40 something years old).
As you may have noticed, the pricing is a lot higher than the cruises on either side of the holiday period.
BTW, I saw that you posted the same question in another thread. I deleted that message. We prefer that a question only be asked in one message thread, since duplicates just add to confusion.
Thanks for posting on cruise-chat!