Give up the chaperone commitments for sure! The leaders can find back-up. This always happens--always, everywhere. Make that call ASAP--"I just can't do it. I am so sorry. Something has come up in the family."
Next, do you have a co-worker/chair for the Christmas event you're scheculed to run? Call her--same thing, maybe help her find help--but you get out of it. If you don't have scheduled help with that, call the school secretary, she can help. Same script: "Something has come up in the family, and I am so sorry....(if they are butt-in-skis you add: "I really appreciate your concern, but I just can't talk about it, it's too upsetting right now.")
Things happen, schools have lots of safety nets--and I know this...I've taught in three different schools: everyone can adapt.
You have decide about going to the kids' room parties. You can still go, even if you've cancelled all else---------because of the nature of the script you've used---that's why I know this script: it's the one that works, it's the one that honors your privacy. If people don't respect that the first utterance, you repeat it again--don't give in.
Do you know other parents who will be going to your kids' holiday parties? If the parties are separated by days, and if they are down the road, it's not a given that you won't make it to them.
But the chaperoning and the organizing? You can take care of those burdens--as in hand them off to someone else--right now. Please do that. It really is better for everyone, even if it doesn't feel like it now.
Get those calls made right away and get those concerns off your mind. Please do this.