Treat the other parent with respect. Keep the other person informed. Allow the other parent to inform you and update you without conflict. Be polite to your co-parent's new partner. When your child complains about the other parent, ask questions rather than jump to conclusions.
Children are capable of playing games, too.
Your child will ask about the break-up. It is helpful if both parents agree on the same explanation. Regardless of age, children need to hear that romantic love can end, but parental love does not. Tell them again and again. The Traverse City Record-Eagle.