Party Tonight!!!
You definitely want to see the parade and the fireworks. Those are can't miss.
The rides are there, but you can do rides anytime. However, the lines will never be shorter.
As for characters, why not concentrate on the ones you wouldn't normally see: visit Jack; Pocahontas & John Smith; Pirate Donald & Pirate Goofy; Pirate Mickey & Pirate Pluto; Princess Minnie; Princess Daisy. Belle has a different setting in her Fairytale Garden, so that could be a nice photo. It is easier to find Snow White in Toon Town because she is with Cinderella and Aurora, however, if you've seen them already, you could skip that line because they don't have different dresses on. The same holds true for Ariel and Jasmine.
Aladdin and Jack each do a separate show in Adventureland.
There is a dance party in Tomorrowland with Stitch and Chip & Dale. There is a dance party in the Grotto with Sebastian and Flounder...I think.
And I would definitely get a photo with Cinderella's Coach by the fantasyland skyway building.