I think the letters to your children were a nice idea.
I am finding that saying and doing nothing works better to get me what I want then saying the things I really want to say...you know the ones that we role play in our mind. Not saying anything is my 180.
When we were trying to figure out how the kids will spend christmas, I just wanted so badly to rub it in and make a comment like " you and your mom thought divorce would go over smooth and easy, how's it working for you? Kids don't want to see you for christmas". Or " did all your friends and supporters tell you how hard the holidays would be, or how hard it really is on kids...not that your decision was made based on them?" Or "I'm the one that does the daily grind. You chose this and now you want them christmas? What about all the other days of the year"
Instead I just kept quiet and let him know how hard the back and forth would be on them. And you know what, he decided it was best for them to stay with me and just visited in morning before our parties started.
I think if you back out graciously and just give husband the time to reflect, instead of giving him a person to oppose it will work better for you.
Oh how I wish we could say those examples you give in your post JulieH! I've said all of those in my head when trying to sort out Christmas too!