Since we'll be driving in, it looks like we'll have trouble finding somewhere to park our car for the FReep. I hope that's not the case. I'd hate to be caught in a virtual loop and have to drive around and around the FReep for 3 hours. :-)
Don't drive into town. Stop in Virginia at one of the Metro stations with parking and take the metro in to the Smithsonian station. .
Here's the map
http://www.wmata.com/metrorail/systemmap.cfm