They just need to build a bridge. I don't care if they make it a toll bridge and match the current exorbitant ferry price - so long as you don't need to sit in a queue for 3 hours only for the ferry to then break down.
I'll second everything FalcOn has said. With the rain we've had recently, the Creb will be closed, but Bloomfield is a nice drive - the 200 will eat it up. As has been mentioned Woobadda ck is my favourite place to stop. If you make it all the way to Wudjal Wudjal, turn left as you head over the causeway and follow the track down to Bloomfield falls - it's a beautiful spot. Just watch for snakes and crocs.
It depends on how much of the day you want to use, as to whether you cross the ferry or not. You can still have fun south of the ferry if you only want to be away from the spa for half the day
. As FNQBuntip has said, plan for long waits at the ferry, so count on being over there all day. The other option is to come back late - when we were up there visiting friends a month ago we came back over the ferry at about 10PM - had the "boat" (I use the term very loosely) to ourselves, but still needed to wait 10 mins for it to come get us.
Cheers,
Matt