There is certainly no information out there to suggest a Z3 is an unsafe vehicle. I wish the best of luck to you, your son, and your estranged wife in resolving this issue that reminds us that divorce seldom ends problems. In many ways, it only exacerbates them. I hope you and your son enjoy your time together. It sounds like you already know just how important it is. You may also, and this is just a suggestion, want to seek some professional help in reducing tug of wars like this from happening in the future. Whether together or apart, you are still a family. Hope this helps. Please forgive this unsolicited advice.