Lots of good stuff to be found at Chadwick! There are 125 miles of marked trail and some good single track to be found also. It is mainly all rock, from gravel type fast stuff to ledges etc. It can be ridden in the wettest of times so don't let rain worry you in that area or WRM, both are best w/moisture!!
If you drive another hour or so south, go to Fayetteville Ar, 27 miles east of there is White Rock Mountain, beautiful stuff for sure. A bit more technical than Chadwick and much more scenic ta boot. Hopefully someone in your group will have a GPS!! You may try to contact JEB, he is a member here as well as a few other sites. They just finished a ride at Chadwick and WRM, he could further define some of the areas they rode. I will be out of town that week or myself and CRSwade would join you guys!
Brian Jahelka from the BlackJackEnduro website is another great contact for both of these areas. Go onto that site and he is the webmaster, good luck and have fun.