Since you are going to be in Florida, I recommend you visit Siesta Beach (
2nd best beach in America) in Sarasota, and Cocoa Beach. Siesta Bch is 2 hours away from Orlando via the Interstate, and Cocoa is about an hour away.
Cross check the dates you are going to be in Orlando with
NASA. If you have the chance to see a shuttle launch, definitely take the opportunity!
As for things to do in Orlando, City Walk is nice as is International Drive. Downtown has a decent nightlife and good food.
If you decide to spend some time in Sarasota, let me know. I'm pretty familiar with the town and I can recommend lots of things to do, great places to eat and drink.