Well, check with an attorney, but I think you're out of luck in terms of legal remedies. So, that means you have to rely on having a persuasive child, as hard as that sucks, if you're getting resistance from your ex.
I'm actually surprised you were able to do this on line without a comprehensive parenting plan that asked about things like that. My first marriage was just paperwork to end it, but we had no children and no joint assets, but the other one required a small fleet of attorneys at least in part for custody and support issues.

