As kml said, without a court order there is really nothing you can do about W, OM, and the kids.
Attempting to reason with her, make an arrangement, or alike, is futile; and most likely will be used against you. I am sorry to say it is best to just save your breath.
If the children are being mistreated or such, then most definitely get involved and get legal protection. Most MLCers do not get to that point. However, quite a few do try to limit their responsibilities, which includes the children. What was the custody settlement?
Hamburg, the pain and sting does pass, fades out of the everyday, and even out of recollection. You are getting closer every step, and every day.
DnJ
Feelings are fleeting. Be better, not bitter. Love the person, forgive the sin.