I've been to the Whitsunday Event a couple of times. It's a good fun weekend. I'd like to go again this year, but I am not sure I can get there in time.
On Saturday arvo they have a pretty causal (think NQ) Show N Shine at the nearby ex-dam workers camp. It's casual, but the bikes on display are often very nice indeed.
Sunday is racing, the event is a regular open MX event which includes and features Classic Racing classes in the program. The times I went there were around 200 riders all up, with about 50 Classics.
The track is natural terrain, without any artifical jumps at all. Would be fun to ride for sure (I don't ride anymore).
All in all the friendly, easy going nature of the event (and officials) along with the location make it an unique event which is worth going to I feel if you like something a little different.