That trick of going to the 'back' of the park *first* and working your way back to the front really helps (besides, you're closer to the entrance when you're tired! LOL)
Remember, City Walk is FREE (that's the outer part of Universal) - tons of shopping and food and the movie theatres. Themed restaurants (Hard Rock Cafe, NASCAR Cafe, etc.) and you can do that at night *or* during the day.
Epcot has the best fireworks at night, but Magic Kingdoms are no slouch either. 9:00 I *think*.
Either park will tell you where the characters will be if you want autographs. Ask at the gate. At Epcot they have set times when the bus of characters comes in, so you can be there early if you want (I *think* they're still near the big fountain just behind and to the right of the Epcot silver globe.
Did you go thru Spaceship Earth? Did you get your pictures at the end and email them to yourself?? That IS fun.