Sorry to hear of recent events. I'm not at all surprised to hear that your S9 is aware of what's going on. You don't have to tell your kids about their mom and OM; they will figure it out when they're old & mature enough.
I'm not sure that night you were talking about when S5 changed his mind was "your" night or not, but if the kids are scheduled to spend the night with you then I don't think you should let your sons pick which parent to stay with, and they should be staying with you. I think that isn't good anyway, consistency is better, and made worse by the fact it's apparent your XW is bribing the kids to ensure they spend the night with her. I think it gives the kids more power than they should have. Your S' are old enough to stick to a schedule, and I should think the parenting coordinator would back you up on that too.
I know it's irritating b/c of the crappy parenting our X's do and the over-focus on their OPs, but you have to let it go. It's not good for you; she is not being a good mom, accept it and just work on being the best dad you can be!!! Re: the boy scouts; make sure to take them every time you have them, and on her nights let it go. You just have to focus on you and your boys, and not focus so much on your X and OM. I know that's easier said than done!!! ((((((((((((nc)))))))))))
