That week is officially the last week of spring break, so it's believed to be somewhat crowded.
Best advice I've seen for going at crowded times is to go with that in mind....so that you don't grow frustrated at long lines, expect them, and be wonderfully surprised when you find a short line!
I'd also suggest getting to MK at rope drop, hitting the highlights, grabbing all the FP you can....head over to DCA when it opens (and remember it's often earlier than the posted time) and hit the highlights, grab FP. Now that you have a few rides done and FP in hand, plan your strategy based on what seems to have reasonable lines.
I found that MouseWait (a phone app I have on my DroidX) was pretty accurate for wait times......and that helps you not having to run across the parks to find the lowest line. Check it as soon as you get off a ride and decide where to go from there.