While I could do two weeks at WDW, I think 7 days would be too much for DL.
I'm thinking if you can wait to do DL after the Rose Parade and other SoCal sight seeing so that you're going when school is back in session, you'll have a pretty uncrowded park.
I like 3 days, but I've discovered that I don't know how to do anything BUT go commando. So go figure.
Honestly... I think 4 would be plenty. About 3 at DL, about 1 at DCA?