My Vernon trail is really nice along the Potomac. It gets a lot of traffic. There is a nice paved trail along the Fairfax County Pkwy which terminates just north of Ft. Belvoir. I bet there are nice trails in Mason Neck park. Fountain Head Regional Park is known for great mountain biking trails. If you have FB, there is a Northern Va Gravel Group. They post weekly rides out in the western part of the area. Good luck with the move and the post.