When will you go to Aust? If no rush then wait till your new born turn one. It is a lots easier to take care after 1yo up.
Good that you have another elder kid. Train the elder one to look after little one too. I have one 7yo girl. She can take care of herself eg shower, tidying up own belong, set up table for meal, make bed....etc. I also start to train her to make breakfast every weekend - pancake, toast, egg...etc.
No need to resign so early. Just starting to train the kids bit by bit now. You can resign few months before leaving HK in order to start full training enforcement and also packing too.
My girl will start P2 in mid Term entry. However, the school ask us to take my daugther to the english asssessment prior to start the school. I am just wondering what kind of asssessment is that and what level of english proficiency does the school required for P2. Hope I don't need to pay extra :(