Topping up children's SA

As parents, we are allowed to top up their CPF OA and SA? I am thinking of making a top up of $20k to my child's SA account. This is my way of ensuring that there will definitely be some inheritance monies left for my child if I were to pass on and she can use it for her retirement. I know that I can have a will but there are many legitimate ways for the executor / trustee of my child's monies to run it down to $0. What do you think of the idea?