I understand why you want to send the email. I also understand why you want the content of the email to reflect your truth.
While not quite the same, I had a similar issue with how my H wanted to tell our D7 about the S -- specifically, he wanted to tell her that we had decided on the S together. I objected, not because I thought she needed to know that H initiated the separation, but because I didn't want her to be comforted with information that was not true. In the end, we compromised with, "It's no one's fault."
Obviously, what you would say to other adults is different from what you would say to a child. But, if these are mutual friends, and you are sincere in your request that they not choose sides, I don't know that I would want to say in the email that H is the one who initiated the D. That seems like the kind of personal detail that you're trying to avoid by taking out the reference to MC, you know?
Ultimately, regardless of what's said in this joint email, you're going to tell your friends your truth and he's going to tell them his. I'd use neutral language in the email and then share what I wanted to share with people individually.
