western australia-Ningaloo reef and Cape Range NP, Cape le Grand NP, Esperance, Broome, Dunsborough/Margaret River, Kalbarri Gorges (approx.8 weeks)
Queensland-Cape Trib and Daintree, Port Douglas,GBR, Eungella NP and Cania Gorge, Fraser Island, Brisbane,Whitsundays...(5 weeks)
NSW- sydney, blue mountains, (1 week)
Victoria- Grampians, Soveriegn Hill at Ballarat, GOR, Anglesea, Wilsons Prom, Melbourne, Penguin Parade on Phillip Is (4 weeks)
NT- didn't travel as with small kids, will do when they bigger, but have been told excellent trips into Bungle Bungles, Katherine etc.
Try and spend a decent amount of time at fewer stops this will give you better sense of place. We visited above places over 1 and half years with small kids so 6 months of complete travel should easily see all. Again a 'to do' list will depend on your likes/dislikes. We love nature and camping so the NP's of Australia suited us and gave us a good sense of what each state offered.
Happy planning
Puffin