You need to re-frame your thinking.
Don't ask yourself what HE wants.
Don't listen to what he says HE wants.
It's NOT about HIM. From now on, it's only about what YOU want. It's about what YOU think is best for the DC and what is best for YOU.
Don't allow him to try to use your DC to 'influence' your decision making either.
If your kids suddenly say that they want Daddy to come to their house on Xmas eve/day/night/boxing day, simply tell them that this is YOUR house, NOT Daddy's, and that when they see Daddy, it will be at HIS house.
Make it 100% clear to the DC that YOUR house is out of bounds to him.
Make it 100% clear to ExH too by telling him what will be happening at Xmas, NOT asking or 'negotiating' with him.
eg. ''ExH, the DC will be available to visit you from 330pm to 7pm on Xmas eve. You will collect them from school and I will collect them from your house at 7pm. If you want to see the DC, I will drop them at your house at 11am Xmas Day and collect them at 2pm, as we will be going to my parents for Xmas Lunch and supper.
(Or as PP's suggested, giving the choice between X and Y only.)
It's no longer about trying to make HIM happy. It's no longer about doing what HE wants, when he wants etc.
It's about setting the very reasonable boundaries for your new co-parenting 'relationship'.
He will try very, very hard to keep the 'status quo' of him making decisions and you running around pandering to him, but stay strong and ride it out until he has no option but to accept a new 'normal'.
If he can't pick the kids up from school or isn't at home when you try to drop them off, then tough. You just go home and he has to wait for the next scheduled visit. (Make sure he can only contact you through an email address. All other methods of contact stay blocked)
Setting your new boundaries will be hard work, and he'll try anything and everything to try to force you back into the subservient 'accommodate' role he put you in during your relationship, so persistence, perseverance and patience will be your new 'norm'.
Just remember, if it was truly 'impossible' for anyone to 'manage' school pick up's, meals, homework, after school clubs, classes, sports etc, then how the hell do you and countless other Mums manage to do it?? Yep, they simply prioritize the kids needs/schedules etc.
He CAN do it, he simply wants YOU to continue to bend yourself all out of shape, arranging and accommodating things to suit HIM and HIS 'priorities'. (Usually his work and social activities or sports)
You'll soon see how much his DC are 'prioritized' by him.
You've done the hardest part, now at least you have your very own 'safe haven'.
You simply need to keep on keeping on.