You should file for divorce and get a formal child support order. The judge also will give him a visitation schedule of when he can pick the children up but the court will not make him see his children. If he doesn't want to, he doesn't have to. You can't force him be a good dad to your children. He does, however, have to pay the child support whether he sees them or not. He'll have a garnishment on his wages. A formal order from the court would protect you and your kids financially.