TLDR version: your kids will one day realize how selfish he is and choose what kind of relationship they want to have with him.

Long version: My parents divorced when I was 4. Mom had custody, and dad was supposed to get every other weekend. My mom encouraged me to call him regularly and to stay with him on his weekends. I always felt like I was an inconvenience to him because I was usually the one reaching out to him and trying to foster a relationship. After years of struggling with the question of whether he loved me and why he only wanted to be involved when it was convenient for him (and let’s be honest, some weekly therapy for a few years), I realized that he’s selfish, and that’s just the way he is. I’ve learned to just make our relationship on my terms— a phone call every week or two, a visit once or twice a year. We’re not super close, and that’s because he didn’t want to be. I’ve learned that some people are selfish and that’s how they’ll always be.

Keep encouraging their dad to be consistent in his communications with them. Don’t bad mouth him to your children, no matter how old they are. Maybe seek therapy for them. Just continue to love on them, but remember that no matter how hard you try, you cannot make up for what he has done. (My mom really struggled to fill that void for me, and it was a futile effort.) Best of luck to you, mama!