What I am getting from OPs posts is a real sense of her need for control.
She's controlling this thread by telling us from the outset what she doesn't want to hear from our responses. She didn't disclose the age of her kids immediately as I suspect she knew a lot would tell her they are young enough etc.
Then there's the control of this situation - you've got it all planned out - how everyone's going to behave and how everyone's going to react and it'll all be when you say so.
Please don't get me wrong, I'm not trying to be mean, but it's the sense I get from what you've written. My assumption is your need to control comes from the treatment of you by your husband. You're trying to out control him almost.
My ex-MIL is controlling and manipulative, I can see it comes from a place of love, but it's overbearing, disingenuous at times and she's over stepped the mark regularly. My exH has learned from his parents that his father can pretty much do as he pleases and she'll just put up with it.
As a result, he has been really shocked to find that I will not tolerate his behaviour and we are separating.
My parents are separated (I was a teenager) and there was always a sense between us that he was more normal than me because he was from a together family. But actually, as I have more distance from them I see how messed up they are, and he is. And I'm the one who seems to be emerging from this intact and... in control.