Karijini NP. Tom Price is worth a visit, great little town. Cape Keraudren, just north of Port Hedland was awesome, we were the only ones there over looking the ocean. We loved it in Broome, very laid back lifestyle and theres a nudist beach that may interest you?
El Questro was really nice but its closed over the wet. Edith Falls 60km north of Katherine in the NT, may also be closed over the wet. Apart from the heat you two are generating in Geraldton,
it gets much hotter further north.
Ps: Don't bother going into Onslow, it's not worth the drive!