IT IS NOT RUDE TO TELL YOUR DAUGHTER THAT IT IS HER RESPONSIBILITY TO ENTERTAIN HERSELF, HER PARTNER AND HER PARTNER'S MOTHER, ESPECIALLY SINCE HIS MOTHER WAS INVITED BY YOUR DAUGHTER AND NOT YOURSELF.
You were expecting your daughter and her partner to come for 3 or 4 days, and you weren't expecting his mother for 3 days at all. Your daughter took it upon herself to invite her, and bounced you into nodding along.
It is all too easy for adult children to revert to their child-roles when they visit, but you need to take your daughter to one side and explain that due to your current thyroid issues she needs to step up and be an ADULT during this visit. So - no sitting around expecting mummy to do everything, she needs to step up, roll up her sleeves, and HOST. Because you NEED to rest, no ifs and no buts. So - you said on the other thread "i also know that they will want usual Christmas things like games nights , buffets , film nights. I think its because it will be 9 nights that feel mentally overloaded." Fine. but they should not look to you, with your health issues, to be doing this for them. They should arrange all this themselves. I'm sure they're capable.
You also said on the other thread "we and the partners mother live near ish each other". I think that you should suggest to your daughter (and when I say 'suggest', I mean 'tell') that when his mother goes home after her stay - THEY GO WITH HER. After all, surely her partner would like to spend a couple of days at his home in the same way that she does? And maybe they could fuss over his burnt-out mother instead of expecting you to do that? They can come back after giving you a couple of days not feeling like you have to host, but nine unbroken days is beyond your current energy levels.
As for your son, I don't know how much work he is, but again he should be taken to one side and told that your health must be your current priority. I don't care how demanding a job he has, he doesn't need you skivvying after him, he's an adult. He might even enjoy skivvying after you!
You don't mention a partner, OP. Do you have anyone you can share this load with, to back you up should your daughter start channelling her teenaged self?
[ Link to other thread for others to find details of the full situation. ]