I have to respectfully disagree here. It is not better for them to have someone acting as a father or step father that is not their father. It further damages them. I will not be working with this loser. My kids will know that he is trying to help keep their parents apart. I will not be expecting them to show him any respect at all.
It sounds like you are wanting your kids to be vindictive. And that you are wishing you could control your children's attitudes towards the OM.
As far as going for full custody based upon introducing the kids to OM - I've been there. My L told me that I had a great chance at full custody because of her and him exposing the physical aspect of their affair in front of the kids. But in the end, I dug down deep and realized I did not want a fight and what was best for the kids. In the end, I talked with OM and he is an ok guy and the kids get along just fine.
As much as you may despise what OM is doing, you gotta let it go.
Also, if you do get divorced, remember that you may find someone else and will also maybe someday introduce the kids to that person.
