As I said on your other thread, the letter you wrote for the teachers is way over the top. And you aren't fooling anyone -- you mean it as a message to W to make her "wake up." Just stop trying to make her wake up and see the light. It does NOT help. It is pure pursuit which will get you only more pushing away.
Do NOT send anything to teachers until you tell the kids. Moreover, this is really nothing to put in writing. Geez. AFTER you have told the kids, set up a meeting with the teachers:
"Teacher, we have told the kids that W and I are separating on April 1. It is a difficult time that will be hard on the kids. Thanks so much for the important role you play in our childrens' lives. Please let us both know if you see them struggling. We welcome your thoughts on how to help them succeed in school through this process. You may contact us at this joint email address: xxxx."
