MIL driving me mad

I think the idea of a hotel sounds fine. If you feel you want to explain to MIL, text her or email.

Use the time alone to rest and think how you want to go forward in your marriage. If you don’t want to go straight to divorce, plan your strategy and tactic for relationship like it’s a high priority task at work.

Are you going to tell us what happened? Please do !

She thinks she's stepping up which is what he guilt tripped her into doing. He's being terribly entitled if he can't see why her taking over your kitchen on 23rd is OK. It's pretty much his domain to sort this out !

I think the OP was saying this was the first she had heard of it being a family tradition? Not that first she'd heard of biscuit decorating per se!

Message MIL saying what a lovely idea but your kitchen will be in use in the lead up to Christmas with meal prep etc so you'll be dropping the kids round to her on the 23rd, don't ask, tell her. Leave the ball in her court. If she's so excited she'll be happy to bake with the kids wherever. If she pushes back saying that won't work suggest a date after the holidays that'll work for you then when she's baking with the kids have a day off to relax. Meet a friend for coffee or do something you don't usually have time to do. As you're leaving light heartedly say you expect the kitchen to be pristine when you get home so she knows not to leave a mess.

You absolutely have to go out!

You’re going out to do some last minute shopping (or a wine with friends) while they do it surely?! Bye mil, have fun!

Tell her Dh will be delivering said grandchildren around at teatime-she can have tea with them and DH, and then do the cookie thing. Then she can clean up their mess. Pack them off with their nightwear- as I am sure they will be tired after baking with grandma!, and then DH can pick them up the next day! Tell her the kids are thrilled to be staying at grandmas! You, put your feet up and have a night off!

Why is no one throwing this back to her?
Thank you for the invitation to bake cookies with you, as you know I am too busy to accommodate that day, what time would you like the children dropped off at yours? And leave to your husband to argue as its his mum.
She will do this every year if you allow this. It's more the fact that you've said no and been ignored by her and your husband. Whatever your reason to refuse was, it's your home. You've said no and that's the end of it. I can't imagine being entitled enough to argue with someone over me forcing myself into their home when it's not convenient.

Have you asked why she doesn't want to do it at her house? If she hasn't had them much it might not be young child friendly, no stair gates / glass coffee table / weird ornaments. Or it might be that she isn't confident with them alone or is worried about nappy changing and would be fine to do it at hers provided your husband stayed with them? I would either way just leave it to him.

I’d make it clear to DH that I will not be cleaning up after the mess. Let him know that he and his mum will have to clear up the mess as your going for a nice bath

I'd die on it.
Nobody tells me whats happening in my house.

Is your husband going to be home when the proposed cookie baking takes place? If so, you can remove yourself from any involvement. If not, you can tell him that you don’t want to be involved so it needs to take place at her house or be rescheduled for a time when he is a at home to host his mother.

much better tradition for it to be a her house and Dh goes to help supervise.

keep pushing, the children will love it, it will be a better treat with the change of scenery and special time at granny's house. lots of lovely memories to associate with her house.

keep insisting its at hers

Well yes - I agree 😂

But it’s more about whether this is a hill the OP wants to die on IF the MIL insists it has to be at the OP house.

I have no idea the bigger context of the relationship and letting MIL dictate is a thin edge of a wedge- so maybe the OP shouldn’t suck it up - but honestly if this is just a minor irritant then I would let her bake and personally fuck off out the house for a cup of tea and book and a few hours of respite from very small children

Why the absolute fuck does she have to suck it up??
If MiL is desperate to bake... do it at her own house.

That's as ridiculous as it is manipulative. You do not get to commandeer someone's kitchen 2 days before Christmas! No, no, and again, no.

I would tell DH that he must have misheard and that the baking will take place at MILs house. I would say that it sounds like a lovely idea but it needs to be done at hers.

Her heart is not in it, she doesn't really want to do it but doing so under obligation as she's been called out.

If she agrees to bake at her house, which you should insist she does, I've a feeling she'll pull out & say she's not well. She can't really be bothered & that'll be her get out card.

It's sad, down to experience unfortunately.

I wonder why it can't be done at hers. Especially as you are hosting Christmas. Anyway, if she does it at yours on 23rd make sure she and dh do prep and cleaning up etc. Maybe go out

I think you're blowing it up out of all proportion.

Let him deal with this. He's obviously got issues with his mother and it's probably best to stay out of it and let them build those bridges. Who knows, it could turn out lovely, especially for the kids.

So he can plan with her, shop, host, prep - and clean up.

Make sure he knows that he's running that particular show. Handover, step away and wish all the best creating a lovely new Granny, Daddy and kids tradition.

Sounds like something husband needs to manage, including clearing up. I,'d go out and leave them to it.

If you don't want to say no, only at your house etc then take steps to minimise the potential mess and get pre made cookie dough. The DC can then cut different shapes and bake and decorate.

Inform her dh will drop the kids over on 23rd or 24th. Which does she prefer?
Did she actually do this tradition with dh when he was a kid?

Don't supervise, don't clear up; if MIL needs help with either, DH can do it. Have you got a friend who would like to have you round for a Christmas drink or something? Enjoy your unexpected evening off.