Huh ... who would have thunk it that the state might write something that would exempt child safety seats. My bad for not considering the absurdity of state legislatures. Show those idiots an image of a young child propelled into a windshield at only 30 MPH and they'd be sold. I still have a few such images seared into my brain, and I would never allow a child to travel without a safety seat or properly restrained.
I would honestly have to say that if I were mom I would also decline to allow my child to go into such a vehicle without proper restraints come heck or high water. And, personally, I doubt that (a) any officer would forcibly turn the child over to dad (they would likely file the allegation of contempt with the prosecutor), and, (b) that any prosecutor would consider filing contempt charges for a mother failing to turn such a child over.
Since it appears dad has access to another vehicle, mom should go BACK to court and mandate child safety seats in the visitation agreement.