I was on Wonder last NYE. The special things that I can think of are : a special lithograph given to all guests, a box of chocolate truffles and a giant Mickey head in chocolate, free champagne on deck before the NYE fireworks and countdown, NYE hats for everyone, a deck party after midnight. The Christmas decorations were taken down between the previous cruise and ours - we sailed on Dec. 30th.
All in all, it's probably the best place to celebrate NYE with your family.