4 Weeks in NY, VEGAS, LA & HAWAII

We are heading to the US on the 22 december starting in NY for xmas, then on to Vegas or New Years, the LA & Hawaii to relax on the way home
We are doing alot of various tours, disneyland, san diego zoo, universal studios, sea world etc
is there any other suggestions of things we should definately see and do while we are there?
Any suggestions on a good spot in Vegas for New years??

We are from australia and this is our first trip overseas .... any suggestion would be greatly appreciated

I know most flights to AU depart from LA, but I would not spend too much time there (not the nicest of cities). I suggest you make a change or 2 to your itinerary to include the nicer places on the West Coast such as Seattle, Portland or San Francisco. Boston and Washington are also great places on the East Coast. New York is ok for a day or 2, but it's SO VERY EXPENSIVE! If you like snow/skiing/gambling try LAKE TAHOE near Reno, Nevada (rent a car in Vegas and stop on the way to San Francisco).

Remember that our seasons are reversed from yours. December and January are winter months here. Speaking as a former resident of the Seattle area, avoid the Pacific NW and Portland during these months due to their awful weather.

You'll find NYC cold and possibly snowy but it's a great town. Las Vegas will be dry and cold at night, typical for desert winter climate. Los Angeles will have fair weather, and San Diego will be fantastic.

In Los Angeles, aside from amusement parks, try some cultural attractions. The J. Paul Getty Museum is a can't-miss.
http://www.getty.edu/museum/

In San Diego, do see the Zoo. The plant life on the grounds is an attraction by itself. Spend some time along the sea in La Jolla. It will be shirtsleeve weather. Sea World is on Mission Bay.

Have fun.