I'm not sure that getting a club in is the right model for a commercially run camping ground.
Obviously Toowoomba mtb club is the closest, but it seems they focus their trail-building activities on Council-owned land.
http://toowoombamountainbikeclub.blogspot.com/
Out near Warwick, the Olomans built their own trails on their own land at Raleigh Park. It's a nice loop too (or at least it was at the race in 2010!) http://www.delxc.com/
And The Riders Club hold some of their races at Adare, which isn't a million miles from Murphys Creek. http://www.trc.org.au/
But this seems to me more likey to work as an Old Hidden Vale type of thing, maybe on a less ambitious and more affordable scale. Get a Pete Wilson or a Roadie Rob in on a paid basis to build some trails, and open it up to the mountain biking public as one of the attractions when you camp there.
