Hi Cara,
Would highly recommend this caravan park at South West Rocks
http://www.horseshoebaypark.com.au/
Other stop off places on the way up from Sydney to Brisbane.
Port Stephens (they filmed some of the beach scenes there for the most recent tourist ads.)
Sawtell (another great caravan park
http://www.sawtellbeachcaravanpark.com.au)
Byron Bay.
I don't know the road south of Sydney that well but I do remember some stunning parts of the coast (take the coast road not the highway).