I can't think of a single situation in which not having a father around who is as thoughtful and careful as you would be a good thing. I know it will be hard, but I think you need to be there for both children. If she ever wants you to sign over parental rights, you can make the decision then, or if the child is old enough, he can make that decision. I still think you need to be in your child's life. Children in this situation seem to think things like "what's wrong with me that my daddy doesn't care about me?" he won't know you're trying to simplify his life. He'll think you've deserted him.