Two more suggestions for you:
1. Go west along the coast, as ang737 suggested, to the Twelve Apostles.
Fly to Tuki for lunch - if you're comfortable with the one way sloping grass strip. Sheep station and trout farm.
http://www.tuki.com.au/
If you can tear yourself away from Tuki its a short flight to Ballarat and taxi to Sovereign Hill - find it on the internet.
Alternative to Ballarat is the RAAF Museum at Point Cook.
2. Fly direct to Asses Ears Lodge. Steve will organise horse rides, 4WD tours, lunch, rock climbing etc.
http://www.assesearslodge.com.au/
There's even a photo of me sitting outside the lodge.
As close to the Outback as you'll get in a day trip from Melbourne.