It looks like Pierce may fill up quick, so here are the other sites.
Green's Lake:
34.979478,-92.385621 - Google Maps

Dix Creek S/W:
34.994151,-92.384744 - Google Maps

Dix Creek S/E:
34.993284,-92.378225 - Google Maps

Pavilion and sites with electric:
34.992815,-92.359629 - Google Maps