WILL- Widower, 1 child, future grandchildren?

This simple Australian last will and testament is designed for a widower who leaves everything to his only child who is at the moment childless, but the widower makes allowance for the possibility that his only child might pre-decease him and at the time of his death may have children of his/her own. He therefore allows for that possibility and divides the residual between that/those child(ren) (in equal share), else another person. It can be easily completed as a form on the screen and then printed and signed by the testator and two witnesses.