Lots of good advice on here, I like Urmstongran’s suggestion, say you’ll do it one last time, and never again. Then buy the frozen this, that and the other as many have suggested, to cut down the work on the day. Maybe even set the table on Christmas Eve so you don’t have to think about that on Christmas Day.
My dear mother told me when my first child was three, that she wasn’t going to cook any more Christmas dinners now, as she was too old, and she’d got two married daughters and she (and my Dad) were going to spend one Christmas with us and the other with my sister. There were no ifs, buts, or maybes, that was what was happening. At this time she was 53 years old!!! And she lived 250 miles away from us, so if she spent Christmas with us, it meant a minimum of a weeks stay. Mum never was diplomatic!
Anyway we accepted what she said and they came to us until five years ago. My parents in law came the year they were at my sister’s.
However, now I reap the benefits of our example, we are now at one or other of our children’s houses on Christmas Day. But I did enjoy all those Christmases, complete with my rather bossy Mum. Sadly Dad is no more, but 92 year old Mum goes with us to whoever is hosting each year as she now lives only ten minutes away from us.