Run some numbers carefully before you turn up, and I would have a cash pool before I arrived also. This is a very expensive country to currently live in, a family needs a household income be it single or dual, of at least 150k.
100k is the new 60k, so 120k you are borderline or going into negative expenses. Rent in Perth for a 3 Bedroom is $600-$700 per week. Grocery Bills $300. Fuel $100. Kids Misc expenses $100. Bills pro rata $300 per week.