This person's
blog has information on all of the CG's around DC.
I have stayed in all of them. IMHO, for a first time visit, I recommend Cherry Hill Park. It's the most popular one around and it is the most convenient to the Metro that takes you downtown.
If you can do without hook ups, there is Greenbelt National Park that is also close to the Metro.
Dave
Mary, the world's best wife (1951-2009) R.I.P
Lizzy (a Boston)
Izzy, Pepper & BuddyP - Gone but not forgotten
2005 Itasca Suncruiser 35A
My computer beat me at chess once; but it was no match for me at kickboxing.