How long are you staying?
We were there for only two days. We left DL the first day after lunch at the BB at 11:30 am.. we grabbed another FP (For SM, I think) and headed over to DCA as DL started to crowd up.
The next day we collected a few FP and rode stuff then collected another FP and headed over to DCA a little ealier becuase most of the things we had left to do were over at DCA.
But I think most of the tips say to begin before Rope drop at DL then do it early and head over to DCA around lunch-ish. But if you have the time you might want to spend one day doing a rope drop over AT DCA.. that would be kinda cool
For the crowds: We were there peak season in July and it was DEAD DEAD DEAD on Sunday and picked up more on Monday (course no days were NEARLY as dead as reya's mommy's trip... that was magnificent)
If you do the park(s) well enough *hydroguy's tips - then you should be fine no matter the crowds.