Matthews Hill Loop via First Manassas Trail
This is one of the best beginner hikes in the area. Don't be fooled by the Difficult rating. It is relatively flat (be careful of the steep hill approaching the visitor center near the end). If you are interested in history, particularly the Civil War era, this is a fantastic area to explore. Take some time to wander down any of the myriad side trails to see historic locations, buildings, and armaments. The newly renovated Stone Bridge is not to be missed.
The visitor center has a sufficient parking lot, however, on nice days it can fill quickly. If the parking lot fills, consider parking at the Stone House around the corner, or further up Sudley Road at an alternate parking lot.
This is a fantastic hike for kids. There trails are relatively flat and there are many fascinating historic sites to see. Highly recommend for children. 9/10.