If your children are too young to make this clear to them then make sure the child is never left alone with the dog.
It’s better to prevent that to cure. When you haven’t children of your own but you know the dog will come in contact with children, than teach him from an early age what children are.
Walk past an elementary school when the children are out playing. Let the boy or girl next door give the dog a biscuit, so that the dog learns that children are fun, instead of scary.
The same rule applies here: what’s learnt in the cradle lasts till the tomb.