As usual, good accurate advice from 404 and Dan.
BTW, are you married ? If not your partner won't be recognised by immigration, there is no such thing as " defacto " in HK. Unless she can get sponsored in her own right ( eg doctor, lawyer, finance, teacher ) she will have to leave HK every 3 months. Also chute, I have no idea what/if your family plans are but try looking ahead a little, is the HK lifestyle ( pollution, crowds, lack of parks/playgrounds ) what you want for your kids ?
Take the pain in Oz early, do the hard yards, in less than 10 years you could have a jet command with an LCC " struggling " on circa 200k/year, or you could be a CX F/O possibly 5 years from command wondering how you can " afford " to come home.