So. My children's dad and I have split up and have been for over a year now. But our kids are 3 1/2…

So. My children's dad and I have split up and have been for over a year now. But our kids are 3 1/2 and 2 1/2 and we're doing potty training. They do awesome when they are with my or my boyfriends family, but I'm worried about when they're with their dads side. Any advice on how to make sure they continue with what we've been doing? My ex's girlfriend does excellent with them and calls if she has any questions on how I've been doing things. But I'm just worried that where we have come so far while I have them that they will go to their dads or nanas and they won't stay with what I've got going. It's stressing me out!!!