Hi Headisspinning, so very sorry to hear this.
When our marriage ended, my ex was rather slack with visiting commitments (last minute changes, coming late etc). One child made excuses for him; the other became angry and refused to talk to him, let alone visit. Also threatened to run away if forced to stay with him for weekends etc.
I urged the ex to be patient rather than to try to force the issue but it still took many months.
The reason I'm boring you with this is that the kid was FIVE. I cannot imagine how we could have forced any visits at ten or fifteen.
Therefore I'd be with those who take the long term view - ie, let the children know their father loves them and has the door open for them, but leave it at that. Avoid religion when you can communicate, but tell about the fun times with your kids. Given the drop out rate of young jws, I'd hope that time is on your side.
Hugs to you both, Retro