Actually, Carol...someone in my band is an ordained Minister, and does splendid weddings.
Too bad you're doing this during a 9 week gig, r'else I'd say he'd be a great one to do it. :::nudge, nudge:::
As for places, here are some other ideas: You are already looking into the Royal Mile.
Try also the Adelphi Mill. Quite inexpensive, actually, and it's a beautiful space. 2 of my very best friends were married there.
Also, check with NCPPC (Nat'l. Capital Park and Planning Commission). There are a lot of little halls that they rent out for decent prices.
There's always the Maryland Renaissance Festival! Lots and lots of really good music there (and I'll *DEFINITELY* be able to attend!!!!)