We really enjoyed our vacation while staying at the Courtyard by Marriott in Manassas, VA. We used Priceline and stayed for half the advertised rate, which is about $139, which was a real bargain! The rooms are large and kept very clean, beds are comfortable, in-wall air-conditioner was fine, small refrigerator in room was a must for us. Most rooms also have a small outside porch which was an added plus.The hotel staff were pleasant and always helpful. It's located in a nice area, close to the battlefield. Pool only opens from 5:00 p.m. till 10:00 p.m. (not sure why they do that), but fitness room is open all day.
My only real problem was with the slow speed on the in-room internet connection (and no wifi in the room, you still have to sit at the desk and connect your computer with a cable). When I had to get some work done, it took almost forever on the uploads and downloads. I was surprised that a Marriott hasn't updated their internet connections for the working traveler.
We enjoyed the Civil War movie (watch that first) at the Battlefield visitors' center and the tours by the Park Rangers (there are several tours given at the different battlefield sites). Admission is only $3 and includes the video and lasts for 3 days.
We drove about an hour and 45 minutes to see the Luray Caverns in Luray, VA. They are phenomenal! Just incredible. You walk underground with your own headphones for a self guided audio tour (we spent 2 hours, others do it much faster, but there was so much to see). If you have a child taking earth science in school -- this will bring it all to life. Tickets were $23 each, but if you have a Giants Supermarket card (we stopped off at the supermarket on the way to pick one up), there's a half-off the second adult ticket discount. Next door is a car museum (included in the price of admission to the caverns) and we enjoyed the hour we spent there as well (some really old but well-maintained cars of long long ago). There's also a corn maze, but we didn't go through that.
The hotel is only 25 miles from Washington, DC so we spent one day in Washington as well, touring the new Newseum. Great exhibit about 9-11 and a history of news and journalism. Lots of videos and interactive exhibits. Expensive admission (most Washington museums are free) but lots to see. Parking in the area was $22 for the day in a parking lot (street meters are only good for 2 hours, and they are few and far between).