No advice regarding NYE. I'm sure you'll have a wonderful trip -- be prepared for it to be busy and make reservations for meals and activities in advance.

It looks like they have two types of bed configurations - Kings and Two Twins. Personally, I wouldn't book a room class that doesn't have the number of beds I needed. It's one thing to hope for an upgrade from a Superior to a Deluxe and be satisfied if you don't get the upgrade. I suspect it's much more complicated to move from a King to Two Twins. I always book the room class that will meet my needs and then an upgrade (if it happens) is icing.

I also suspect that upgrades will not be easy to come by over a holiday, but that's just a guess.