@techyinaz The reality is you can't make him be a good father. You only can control what you do.
It's not your job to make him a good father. It's your job to not stand in the way of when he does want to be a good father. You always need to prioritize what's best for your children, And unless you can show that he's abusive or neglectful, (operative word being "show") It's a really bad idea to try to keep him from them, especially if he's asking.
But if he's truly not asking, I would just try to create a paper trail. If he doesn't respond to your texts to his phone or email or whatever, send him an email or text saying "I've sent you a few emails and text at this point, please respond if you are receiving them" That way it can never come back that you didn't try to communicate with him.
Your responsibility is to your children. Think to yourself: "is what I'm doing legally sound (Am I unfairly and prejudicially stopping him from being a father to my children?)? Is what I'm doing consistent with my own morals about how I want to be viewed by myself and by other people and most importantly by my own children later?"
If that's truly what he wants to not see them until they're 18, He's not putting his own children's best interest first. You don't need to say it but it's going to be obvious to anybody who knows what's happening and sees what's happening.
I'd say you want to secure child support from him because his responsibilities as a father are not negated just because he doesn't want to participate in the responsibility of being a father. Money is just the tip of the iceberg of his responsibilities. But that's the part that is legally obligated by him. Child support is not about you being paid, It's about his children receiving his financial support.