Great for families and variety
This park just is near enough to Baltimore and DC to allow for a quick getaway and offers a lot to do. There are trails in the park you can hike, run and bike; the lake is small but you can paddle and fish; and, nearby you'll find some great sections of the Appalachian Trail.
The camping spots accommodate large tents if needed and the showers are hot.
Be aware: no alcohol in Maryland parks.