Oh no. NEVER tell them you're going to do it if you decide to. It would just give them a chance to spin it to anyone who'll listen.
I had told her a number of times that I would eventually tell the kids and all it did was make her change her tactics, but when I finally told them, I didn't give her any warning and one day later is when she claims she told OM no more contact. And she seems to be keeping her word, but I guess I'll never know for sure. But it seems she has, at least.
The "yeah, well, I had ENDED IT ANYWAY!" thing is just SUCH classic script, LOL. My wife said the same thing!!! What a crock -- I had JUST seen "I love you so much" and "No one ever did it for me the way you do" TMs on her cellphone, just 3 days before!!