A bit early but looking at a good family bush camping holiday combined with some good wave sailing/SUPing in SA over chrissie/ny and Jan...
Greetings from a windy Melbs (gust of 57kts today!)
Robe is always great fun for a sail and a surf ;)
Keep driving and go to Esperance WA
Just go over the border to between port mac and carpenters rocks. All caravan and camping parks will be fully booked anywhere along the coast that time of the year.
Depends how far you want to drive.
Walkers Rocks on the West Coast is a good spot.