Ex Husband Introducing Rebounds

My son’s father and I have been going through an acrimonious divorce for a little over a year now. He has female “friends” who he’s either dating or wanting to date that just so happen to have kids around my son’s age (13yo). We currently do one week on /off between my ex and me. We parallel parent completely and I’m taking him to court for full guardianship and custody pending the divorce litigation.

I’m extremely annoyed that my son’s father has been taking my son on his dates with his female friends- at least two of these women- with their kids. My son tells me that he’s not interested in going on dinner dates with Emily’s mum and he doesn’t know when he will get to meet Tyler and his mum again.

I’m really conflicted about asking my ex not to introduce our son to women and their kids until they are in a proper relationship; he’s previously pushed back with “they’re just friends so why should we not hang out together” and completely ignored my requests. I’m unhappy about the instability and haphazard haste in which my son is dragged into his father’s rebounds. I also don’t want to get into my ex’s business because I want very little to do with emotionally volatile people. Any thoughts on how to approach this situation with my ex?