found: 10 miles down a gravel road. 32' max rv length.
facebook page: https://www.facebook.com/pages/Shady-Lake-Arkansas/269538703413
shows the road and some photos. Looks beautiful but not sure I would take my RV down that road. Also it says some sites are being evaluated and may be subject to flooding.
34.3628361 -94.0277694 for Google Maps for birds eye view.
Look at DeGray Lake State Park, Lake Catherine State Park. Crystal Springs Corps of Engineers park. About 3 hours away.
Also go to: www.recreation.gov and search for Mena, AR there are 66 campgrounds listed in the area.