Your post here on WildTexas.com may generate some interest, although I need to note that generally we don't permit businesses to advertise in our forums. The fact that you're hanging around to get feedback from outdoors enthusiasts is commendable (and why I didn't moderate the message).
Perhaps our members can provide feedback on what's important to them. For example, with that kind of acreage limiting visitation to one group at a time simply because you only have one cabin may not even be necessary. Many people might be perfectly happy with a "flat spot of ground" on which to pitch their tent at night. And folks like birders and photographers don't always do overnight trips, so your daytime visitation could be a lot more than what your overnight accommodations (cabin, campsite) would serve.
Speaking of photographers, your ranch could join
The Valley Land Fund -- it pairs up landowners with professional photographers and generates some terrific PR for everyone involved (in addition to stunning photographs). Justin and I haven't participated, but it's an excellent opportunity. We learned about it a little over a year ago while talking to a ranchowner we met on a birding tour down in Rockport.
Do you have any equestrian trails? Hikers, bikers and equestrians can share the same trails, as they do in Texas State Parks.
For other ways to get the word out, you should consider advertising in the Texas Parks & Wildlife Department's official magazine (
http://www.tpwmagazine.com/), and other publications aimed at photographers, birders, hikers/backpackers, and if you permit hunting of any kind, hunters. There are many speciality publications in addition to the broader appeal ones.