We made a return trip in the late fall to Mt Mag and ended up in the unofficial campground on the back side of the park.  The sites had a table and a fire pit along with a pit toilet.  Mt Mag has some amazing trails and view to explore.  The park also has a lodge if that is your thing that over looks the Arkansas valley below. The staff at the visitor center was friendly and helpful in directing us on which hikes to take in the area.  I would defiantly recommend making reservations if you want to stay in establish camp.