I genuinely don't know and would appreciate other viewpoints. I have four siblings and we all have partners and kids. My DM and DA both suffer from dementia but the early stages of it - they don't know what day of the week it is but know who everyone in the family is. They live in a home 80 miles away. My DB and SIL live nearby and give a great deal of their time to the two old ladies - DB pops into the home at least weekly and he and SIL (who is delightful!) have them to lunch every Sunday. They are having them both over on Christmas day as well as SIL's parents and all their own kids. As a family we have never all got together on the 25th (my mum refused to be a MIL who kicked up a fuss about not spending Christmas Day with her married offspring and actually probably went too far in the opposite direction) but always get together (anything up to 25 of us) a few days later for a lunch and present swapping frenzy. We have done this since the late 70's. This year a decision has been made to leave the two old ladies out of this lunch because my SIL wants a break (she and DB would top and tail the day with an hour's drive each way with the old ladies in the back seat telling the same stories over and over and over...)
On the one hand I completely understand my SIL's viewpoint. On the other hand DM and DA are going to know there has been no family gathering and, even if they don't work out that they have been left out, I think they will be really sad to not see the whole family as usual. And I am not comfortable with hosting a family get-together from which my Mum has been excluded. Or of setting my son the example of treating slightly irksome older relatives this way after a lifetime of loving us all when we were young (and equally irksome!) I don't know what is more unreasonable - to just go along with this and exclude my DM from what might (but probably won't) be her last family gathering. Or to pull rank on the basis that it's at my house this year and insist my DM and DA are brought along too. Comments please!