I hate to say it, but from my experience of WAH's and OW they do whatever they want, they will expose your children to whomever they please, and you really don't have any say in it unless there is a possibility of it endangering your children. I'm not talking about the fact that all of this is going to confuse them and possibly cause mental damage. We're talking about physical harm.
Your H is trying to make you the bad guy. He wants to goad you into saying he can't see his children if he decides to spend the day with OW. Don't fall into that trap. It will only make things worse in the end between you. One more thing he can dangle over you during D proceedings.
I think putting this decision back on him and him alone is exactly what you should do and leave it at that. He has one day to figure it out.
Yes, this is extremely hard, but as you said, you have zero control over what he decides to do. He will face the consequences of his own actions. Maybe not now, but someday.
Go about making your plans, make sure to make them so that they can include the children or not so that when your wishy-washy H finally figures out his own mind you are prepared.
Regardless of what he decides, make sure that you make this time of year special for your children and for you. Leave H to twist in the wind with his uncertainty. Not your problem!
T19 M15 S19 XH47 M43 bomb12/4/07 PA5/07 S12/26/07 D final 11/17/08 Back together with no defined R 05/2010 confused....to say the least!!!