I live in Oklahoma. My ex-wife has primarily custody of our 3 children. One of which is special needs. She on multiple occasions has dropped them off at my front door with no advanced notice and them just knocking on my door and her pulling out of the driveway. They have told me how this makes them feel abandoned and left. She wont tell them or me where she is during these times and rarely shows back up at an agreed upon time to pick them back up. What do I do to get them back?