Should I make a legal will?

my understanding is that without a will the spouse gets $100K and a third of the remaining estate while children share the remaining 2/3rds. I am married have one child with my wife and another child (older) from previous marriage. My work AMP death insurance policy is quite substantial and I nominated beneficiaries as follows: 50% to my oldest child and 50% to my wife (for the younger child). If I die without a will, does this split still hold? If not should I make a will? Can a will include death insurance policy? advice much appreciated.live in western australia