It's a reasonable compromise, yes, but please remember you are not dealing with a reasonable person.
His concern is not what's best for the DC, and his motive is inconveniencing you.
I feel that by rearranging your schedule you are making a rod for your own back. Why on earth should you go to such trouble, he would not do the same to you.
and he may still find a way to muck things up.
But... you have been managing this selfish man's behaviour for years, you know him, your kids and your situation better than us...
Another thing to consider...you seem to be trying to protect your children from being disappointed and let down... but that sadly I don't think you always will and at some point you may need to stand absolutley firm and "allow" that to happen.
Remember I am the daughter of a man who is very similar to your husband, from what you have written about him. I really wish I had worked it out sooner how much of a loser my dad really is. It took me until I was 39 because no one would ever stand up to him, no one would ever say out loud who he really was and what he was like. I wish I had known sooner, and the sooner the better.