Just curious, but since you've been in Australia, have your children starting speaking with an Australian accent? If so how long did it take? They say children pick up the accents first.
My son on our last 2 trips to Australia started speaking with a broad Aussie accent (or at least his version of one) after a couple of days, which cracked us up. Think he was trying to copy his cousins. I kept telling him to stop but he denied he was speaking any differently!. Luckily his English accent came back when we returned, else his classmates at school in England would be giving him some stick.