The good thing in this situation is that you can plan. Have a think about shared care responsibilities, any other family members? And also carers?
I say this as we had the same last year with my Nan, only totally unplanned. She collapsed on the 23rd with a twisted bowel. She’s 88. Hospital said it would be cruel to operate, given how frail she was, and by Christmas Eve we were called up to go and say goodbye. I was hosting for the first time, kids were excited (albeit teens), and Nan’s dinner place was set. I didn’t want to be saying goodbye to my Nan on Xmas Eve, nor did I want my children to say goodbye either. So I spoke to her on the phone, told her I loved her, and told her to stop being so bloody awkward as dying on Xmas Eve or Xmas day was incredibly rude. She laughed, told me she would try not to die…and she didn’t. They operated Xmas day.
This all altered our plans for the “perfect” Christmas and it was crazy hectic. My mum, whilst also terribly upset about her mum, had to ferry my grandad around to the hospital on Xmas day. She wanted to spend time with her grandchildren but couldn’t split herself in two. You have time to plan all of this in advance.
Perhaps write a list of what needs to be done, and when. Who can visit MIL on Xmas day, and for how long. What are your essentials that you need to do in order to still enjoy Xmas? What are DH needs? Then you can try plan the day best you can.
It’s an unfortunate situation but these things happen. Despite all the sadness and worry about by Nan, we did manage to have a good day. I got my grandad fed, I made sure the kids didn’t open all their presents without my mum there, and I myself planned to take my children to see their great-nan on Boxing Day, which we did.
My Nan didn’t “die as expected”. She turns 89 in a weeks time. Try make the most of it OP.