Another vote for the hopper.
DL is an amazing place, and probably needs at least 2 days to see it properly.
DCA is not as good, but does have a few great rides - California soarin, Tower of terror and Grizzly river run are all essentials (And screamin if you love coasters) - but with a biyt of effort you could probably knock them off in a coupole of hours.
So, go straight to DL, queue before it opens, do as many of the big rides as you can and use fastpasses, then head to DCA for a couple of hours, then head back to Dl and finish of your rides, see the parade and see the fireworks.
You'll be exhausted but you will have a great day and see just about everything.