Not absolutely sure about VA law, but most law enforcement officers will not get involved with such a dispute, as they see it as a civil matter, not criminal. Unless they observe any abuse going on, then they have a duty to act. She can certainly call them and they may show up, but if you can show proof that you tried to work this out with the mother and she refused, they will probably tell her she needs to work it out for the benefit of the child.
Just be prepared for a little drama if she chooses to create it. But it's not like LE can come and take the children away......they only are allowed to do that in instances where the officer determines the child(ren) are in imminent danger.
Now, she may try to make life miserable for you later, maybe by filing a petition for contempt of court, which you would have to answer. But given the circumstances, I can't see how that would go very far. All this does is create undo stress and waste money better spent on the children (IMO).