I know when the time comes they will be old enough to ask the question on what happened. I also do not plan to lie to my children, but how do you go about nicely explaining that their mommy ruined our M by having an PA? It a tough one for sure.
I'm dreading that conversation, as mine will be a bit more involved. I'm sure she is already filling their heads with crap.
Maybe not mention the PA but tell them it was her decision - ALL her decision? That's a very fine line. Just do what you think is right. They may/may not find out about the PA...I'm not so sure that should be shared with them, but if they ask I most certainly won't lie.
There are moments in this life when you are so confident in the rightness of your actions, that not even for a second do you consider the option that you might be wrong.