OP again. Thanks for the input on Greenbelt. I've booked three nights there, roughly half our stay in the area. No hookups is fine for us, up to about 4-5 days, since I'm hopefull AC won't be a necessity at night.
We removed the TV from our RV, so lights and water pump are about all we use. I installed two golf cart batteries a few years ago, and we've never had a problem being unhooked for a few days, as long as we don't need AC.
Still open for suggestions about places to stay, things to see and do in DC, Annapolis, central/southern Deleaware.
Thanks!