I can’t believe you got that in your divorce decree. What if she remarries?
Be careful about this stipulation. If she settles down with a guy, your son might feel like he’s left out if she is gone when she he is at his moms. If your ex does develop a healthy R somewhere down the line, for your sons sake, your don’t want him left out vacations, events, etc. because of that stipulation.
Trust me. I would have moved hell or high water at first to keep my daughter away from OW. There was a point where it would have hurt my daughter . He married his OW and she has a stepmother there ( who does a good job caring for her) . I imagine my daughter would wonder why her stepmother went to sleep at someone else’s house when she is there......