I applaud you for being able to be friendly with your H. I just cannot see being friends with my W. That doesn'r mean I will be uncivil or rude to her. And I certainly will not say anything negative about her in front of the kids - that would only hurt the kids, and that is precisely what I want to prevent.
I will not be with W on holidays or her birthday or mine. No anniversary rememberance gifts or cards. She is making a choice that she no longer wants those things in her life. It is not seeking retribution against her. It is reality.