WILL- Widow, 1 child, future grandchildren?

This simple Australian last will and testament is designed for a widow who leaves everything to her only child who is at the moment childless, but the widow makes allowance for the possibility that her only child might pre-decease her and at the time of her death may have children of his/her own. She 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 testatrix and two witnesses.