Bits and pieces of background on DH's grandmother have been posted on other threads, but here it is all in one place:
[bg]FIL always has and always will put his mother first, over MIL. This may be correlated with Grandma being a huge special snowflake. She gets her way most of the time, and nobody's allowed to say boo to her or she'll throw a huge PA fit and FIL will go all crusader to fix whatever is making his mother unhappy. Last year Grandma pulled the "It's going to be my last Christmas!" thing again
(link to my previous thread - be sure to see the updates too) and DH went along with it but took her at her word. Not surprisingly, this year she expected us to come up to see her for her "last Christmas" again, and was taken aback when DH pointed out that last year was her "last Christmas" so we made definite plans to be home this year. We stuck to our guns and now the plan is for FIL to drive the eight-hour round trip to pick up Grandma and bring her back here to stay with him and MIL (note: Grandma and MIL pretty much hate each other) for a week over the holiday.
Second half of the background: DH's two sisters live in town near us, but we rarely see them. We get along fine with the middle sister (just don't have anything in common) but his oldest sister royally messes up her life on a regular basis. She has awful taste in abusive guys half her age, and her kids (my niece and nephew) - who are special snowflakes themselves - don't want anything to do with her as long as she has any of her user boyfriends around. SIL1 only keeps in contact with MIL when she wants something, but MIL tries to keep a line open.[/bg]
Because of all this mess, MIL was basically being forced into hosting Christmas this year and was not happy about it. (She hates cooking and entertaining and hates how her MIL, DH's Grandma, criticizes everything she does.) If she hosted Christmas, she'd have to make it a "whole family" thing, which would have to include SIL1 and her current boy toy and Niece and her screaming brat toddler (not his fault, honestly, but still) and Nephew who would rather sit and ignore everyone and play on his phone and Grandma being upset the world wasn't revolving around her and it would have been a huge mess with the potential for a lot of hurt feelings, at the expense of MIL's nerves.
I actually kind of like hosting and needed an excuse to really get the house clean anyway, so I volunteered to have MIL, FIL, and Grandma over to our house on Christmas day. Since MIL's not the hostess, she's not obligated to invite SIL1, and since we rarely see SIL1 and frequently see the ILs, it's natural to make it an "us and the parents" thing and not "us and the entire extended family." We do plan to invite SIL2, but everyone knows not to mention it to SIL1 and if SIL1 gets mad it won't bother me because we don't see her anyway.
The special snowflake here is Grandma. When I offered to host, I told MIL what I would be doing: we're having Christmas morning with just our family, then everyone can come over in the early afternoon and we'll have a buffet of "heavy appetizer"-type food to nibble on while we hang out, so there will be no big formal dinner and no huge cooking marathon and no specific timetable. Grandma said this "won't work for her" - she expects someone to provide a full Christmas spread, complete with spiral-cut ham and roasted turkey and side dishes and fine china, because it's what she would have done if we had gone to her house (true) and therefore if we won't let her host we have to do the same.
Since this was relayed through MIL, I let her have to break the bad news to Grandma
Sorry, Grandma, but I'm hosting this year and this is what I'm choosing to do! I'm trying to figure out a menu I can mostly prepare ahead of time (or things that don't take much prep time anyway), and I don't want to be stuck in the kitchen all day when I could be relaxing. I don't know why Grandma is so upset - she's in her 90's now and eats less than my toddler anyway.