Wish I were still there, I made it to Tulsa in March. The family is still there in the area, but as they are vacationing in Brazil for the summer I've been staying up here. There are plenty of nice places to wheel, like Trees Ranch, Katemcy Rocks 2, a place SE of Dallas I forgot the name of and of course Marble Falls. The abandoned airport you mentioned might just be the 50-80 acres on the side of Skylark field which is the old Killeen Municiple airport. When it rains it gets nice and muddy and the trails in and out are already well rutted so 33" mudders are good as a minimum for that. There is also a sinkhole in the middle of it to play in that usually has some mud in it year round from an underground stream, but the area is kinda small and probably private property but seems to be free-use. We have had several dead bodies show up back there over the years so keep that in mind, but its not Deliverance or anything.
If you go to Trees, you will get lots of pinstriping and damage, its tight. K2 will need lots of ground clearance and good UCP.