It's all worth seeing! We're starting our Australia trip by spending a week there at a friends shack. Most roads are pretty accessible now they have bitumenised a lot. There is a lot to see without spending a lot of money. Places like Seal Bay (where you take a guided walk on the beach through a colony of sea lions) is pretty expensive but it's a beautiful spot and chance to get up some gorgeous creatures. Kelly Hill Caves are probably in the same boat, bit expensive but worth it.
There is a parks pass you can buy which I haven't used but if you want visit everything, it might work out well.
Remarkable rocks, admirals arch, numerous lighthouses, stokes bay (you walk from a pebble beach through a cave to a beautiful white sand beach with a swimming lagoon).
There are many farms, foodie spots etc on the inland area.
I can't help with the caravan park options, I have really only stayed with friends or in holiday units etc.
I'm getting excited just thinking about it! I love it over there.... if you love amazing natural sites, you'll love it too!