It shouldn’t be too crowded during the day so that would be the best bet to avoid the heaviest crowds on that day. Once the after work crowd starts coming in, it will be PACKED. DCA is better than DL, but both parks will be very tough to navigate from early evening on. Local AP’s are unblocked so expect the locals flood in after they get off work.
The 5 freeway and roads around the area are also jammed.