Sorry I can't help too much, but on a trip to Washington I took a long long time ago I drove, but the traffic was a nightmare and parking was a pain. Needed lots of quarters for the meters. Hopefully it has gotten better since then. Just wanted to say do not forget to go to all the museums and monuments, and of course the Vietnam Wall. All of these are awesome and it will take several days. Congrats to your grandson and enjoy your trip.