Boys and Girls who have never been there, do NOT stay overnight in metro DC unless in a secure hotel location. Super high crime areas normally, and people from out of town for this will be particularly targeted.

The best bets are to lodge up along the metro lines running into Northern VA and places such as Silver Spring and further north, and take the Metro in.

The Metro system can normally handle events up to the mid hundreds of thousands, which they get several of every year. If this turns out to be a multi million person event, the Metro is going to be overloaded, so give yourself added travel time. Driving directly into DC in your vehicle the day of is generally a mistake. But some will do this nevertheless.

Otherwise, if you can charter a bus at an outer assembly point, you can bring it into Union Station, where they have plenty of parking for such vehicles. Check and call ahead for any permits and fees. Union Station dumps you right out into the federal district.

Stay in larger groups, particularly after nightfall, and if straying off the federal areas into DC proper.