Not sure I see the problem with the George location for a weekend, especially when the tourists intend to go to Capitol Hill.
There's a nice Irish pub on the corner, a couple of good restaurants just up the hill at Union Station, not to mention the Monacle over by the Senate office buildings. For lunch, there's the buffet in the Dirksen Senate Office Building, though it might not be open in December with Congress probably out of session and lobbying being sort of out of season. If you go, be sure to get ice cream. Two Quail, kind of behind the Supreme Court, is an idine place at this time. It's OK, not great, for lunch.
The walk across the west side of Capitol Hill to the Mall is interesting, and the National Arboretum and the adjacent American Indian museum are special.
If you are there on Friday or Monday, call one of your Senators' office and see if they can do a staff-led tour of the capitol for you. The Senator won't be there on a Friday or Monday even if Congress for some reason is in session, so the staffers might have plenty of time. Find the phone number at
www.senate.gov.
Mind the weather. It can get raw in December. Even in snow and ice, though, I still love to walk in Washington, especially around the Hill.