In the end, from a practical perspective, it really does not matter who is to blame, especially for the kids. I understand the compulsion to make sure the kids know that you are not the one choosing to put them through this, but not only will that information not help your kids, it will hurt them in the end. I was the child of divorce and after a couple of years, all I cared about was that my parents were happy and that they loved me. Someday, when they are adults, and if they ask you, tell them the truth, but for now my in my experience, nothing good will come from such a conversation.