Sorry to read about the OM2 sitch BL42. No sane person would advocate that the sleepovers when the kids are there are a good idea. But as others have said, you cannot control W and OM2 on this one. Detach.
That sitch is one example of the tension between wanting to speak out and knowing that doing so is unlikely to change anything. Here's the thing - issuing orders or directives to do/not do something where you cannot control the outcome is pointless, smells like weakness and leads to further disrespect and not being taken seriously. You understand this. However, expressing disapproval of an inappropriate situation without any directive or threatened consequence is something different. If done properly - calmly, matter-of-factly, with control - it does not have the same downsides IMO.
I bring this up not to urge you to speak out to your W re the sleepovers but to just address the issue more generally as it can be debated as to whether "STFU if i can't control the outcome" is the best play in all circumstances. It's the safe play for sure as it eliminates the downside risks. But for those who are at or can get to the point of emotional control and calm inner strength, expressing disapproval of actions that they strongly disagree with (particularly when it comes to their kids) actually shows strength. Detachment does not equate to head in the sand and ignorance of bad behavior that affects your kids.
You sound like a great Dad. Keep it up. Your kids have one Dad and that's you. They are very young with alot to learn. Saddle up for the long haul and be their foundation.
Don't spin about the summer vacation with OM2. Summer is a long way off and alot can happen before then, not just between W and OM2 but with your own growth and detachment. One day at a time buddy.
Get an exercise program going. Lift if you can. The iron is great medicine.
