Ex moving away

Ex moving five hours drive away after split, back to his hometown but complaining that he will not be able to see our kids 🤔 we have lived here for ten years and it is our children's home. He is saying that he wants the kids to move up there too. Am slightly concerned he would have the kids visit and just not bring them back, is there anything I can do to prevent this? I had originally suggested 50-50 split custody but he wants to move away and have them for holidays ect...