Beerboy wrote:
As mentioned, there are a number of parks less expensive than Cherry Hill. One rarely mentioned is Little Bennett near Clarksburg, MD. You'll want to make reservations because of the holiday anywhere you stay. It's a 15-30 minute drive to the Shady Grove Metro station and parking garage and you can then take the Metro to get into DC.
That's a good option, just be advised that 270 is a nightmare SB in the morning and NB in the afternoon. Between 6:30 and 9:30 expect heavy traffic and slow traffic southbound. Between 3:30 and 7:00 expect heavy traffic northbound.
Another option to consider is Patapsco State Park. Beautiful park up Rt 29 by Rt 70. That allows you Rt 29, Interstate 95 or the B/W Parkway as a north/south corridor. You would have a further driver to a Metro station, but a much shorter and cheaper Metro trip. Coming down 29 you would likely use the Silver Spring station on the Red line, just outside DC. Coming down 95 or the B/W you would likely use the College Park station on the Green line.