Expect huge crowds, but IF you decide to brave it, hit DL at RD and hop to DCA around noon. Hop back to DL after dinner. A word of warning though. Sometimes they shut down the entrance; no hopping and if you leave you cannot return until crowds fall.
I've heard those peak crowds forcing closures cab be 80,000-100,000 people. Know what you're signing onto before doing it. One last word; pray for rain. Rain will diminish crowds. Poncho or gortex and carry on.
We were there Christmas time last year and by 1pm they shut down the front gate due to crowds. We liners had planned well and had the right expectations...but LOTS of folks in line at city hall to complain about crowds. We had a great timebut it was CRAZY