If it helps at all, my H has been saying "We need to tell the kids" for the last 5 months, but he never gets around to it.
I think it's one of those things they feel they need to do in order to get 'unstuck' -and to convince themselves they are actually doing what they think they need to do to feel better about themselves.
And aside from the pain of it, you're right about the sense of relief that not having her in your bed might bring. The tension must be huge.
You can get through this. It's obvious from your posts that you are a decent, thoughtful person who's a great father to a loving son. Those things will never change.