W took S14 snowboarding yesterday with OM. I tried not to react when S14 said his name, but I felt the shift in mood immediately. Not sure how to proceed with that. I don't know if S14 even knows about them or how W behaves when her and OM are with the kids. I don't want S14 to feel like he has to walk on eggshells around me. I'm incredibly angry with W right now. I'm trying to zen myself out right now. FML
Very sorry you had to go through that, but I can relate as I went through it as well. At the time I didn't know if W was romantic with OM or if they were "just friends" but regardless, it really hurts when your kid/ kids tell you about some outing with OM. One thing I can safely say is your S is old enough to know who dad is so be thankful for that. No matter how hard OM may try YOU are S14's dad. I really feel for those who have younger children going through this because young kids are far more susceptible to being brainwashed by a WAS into thinking OM/ OW is an alternate "parent". But once they're teens they see right through that stuff.
As you said, you can't stop W from seeing OM and you can't stop her from having OM around S14. As hard as it is to think about, try and let it go. In my case I was pretty confident OM was going to be kind and respectful towards my kids, so as much as it hurt at least I was secure that they were safe. I did not try to talk to my kids about OM at all, but if they talked to me I listened and validated. On the rare occasions they did talk about it they were angry that they felt like XW was trying to push them to interact with him when they didn't want to. Their attitude was "we have a dad, we don't want or need another one". Eventually XW had them around OM less and less. They never see him anymore and don't really know if XW is still involved with him or not.
So what I'm saying is trust S14, he's old enough to have discernment and he will very likely resolve this with your W without your intervention.
