I used to live on the east side of the beltway and often traveled to Shenandoah - about the same trip you are contemplating. Make the trip any day except Friday - 66W on Fridays, unless it is before noon, is a nightmare. Any other day, hit 66W before 3PM.
If you cross the Bay Bridge to Annapolis around noon, you will do fine. The 'slalom,' the area of the beltway between College Park and the Mormon Temple, is a pain when busy but should be no problem before 3PM. People do drive it fast so stay aware.
It really isn't as bad as people make it out to be. The above advice of traveling between 10AM and 2PM is good.
Oh, if it is raining or snowing or a full moon, all bets are off.
