Drive!! We live off I-83, about 10 miles over the Md. line.
Used to always fly, but last 5 trips we drove. Can't stand the hassle at the airports any more. The extra days don't bother us, plus we have the car at our disposal while at WDW. Also allows for some side trips down and back.
Of course, you'll need to time things to get around DC w/o major headaches---.