I don't see why rush hour traffic on the weekdays is a big deal - go to the Metro stop at an off-hour (say ~10:00 AM), ride Metro rest of the way, have lunch & possibly dinner in DC, take Metro back, pick up car from parking lot, drive from Metro at ~8:00 PM after traffic has died down. NoVa traffic is awful but the Metro should be crowded-but-fine. I say this as someone who attended Obama's first inaugural which was literally the most crowded the Metro system has ever been.
I was kind of assuming the reverse, if anything - I'd be up for doing DC tourism on Friday during the day (I think Dhyerwolf also said he'd be interested in DC tourism?), but then presumably hanging around Shale's house chatting & playing board games on Saturday when the most people are around and thus it'd be the most unwieldly to do sightseeing. Also per notes already made, the free museums in DC will be *packed* on the weekends but somewhat more sane on the weekdays.
On that note... would there be interest in role-playing games for whichever day is dubbed the hang-around-Shale's-house-day? I can easily bring down Fiasco & The Shab-al-Hiri roach, which are super-casual pickup storytelling games, but I also have a Trail of Cthulhu one-shot I've run before and could run again (and I know Shale played in Cthulhu mafia and knows something of the setting). Said one-shot might run better with at least a little forewarning of who the players are and how many. For those that don't know Trail of Cthulhu, the system is *incredibly* light and very narrativist, so there isn't any fear of not knowing the system; the party can fail, but usually by making the wrong decisions, not via the dice rolling poorly.