Op, you're very kind - both to his new partner, your kids (and anyone reasonable can understand why you'd feel such discomfort at him pretending you (or neutral reasons) are why your relationship and marriage broke down, and everyone believing it while he destroyed it by being a scum bag punter) however ....
You're going to have to do it for every fkg gf he gets if you start.
Then there's the fact women love to believe the crazy, jealous, bitter, lying ex script; women fall for that like lemmings off a cliff.
It honestly may not be worth the hassle.
If you want people to know why exactly your relationship broke down, I'm sure there are a few ears you can selectively place the information that he fucks prostitutes whole in relationships (and from the start/throughout) ... People love to gossip, it'll get around. And it should get around.
Fuck falling on your sword for a man. People should know who he is and what he destroyed.