$147 - Roundtrip Flight to Orlando from Washington DC
Need to book soon. Fly on Wednesdays, for the cheapest airfare.
Looks like Airfare is offering similarly priced flights later in May as well. I’ve also found some comparably cheap flights on Tuesdays and Fridays.
Try doing searches on a travel search engine like Sidestep.
Things to do in Orlando:
Orlando has the most rollercoasters per capita in the United States. That’s quite a few rollercoasters. My suggestion would be to head to the Universal Studios first, home to the Hulk Rollercoaster ride (pictures), then make a few days for Disney World and Paradise Island.