MIL makes everything into a grand gesture

OK, your MIL is a total drama queen (slightly enabled by her son) - I would find it very difficult not to challenge the "watching the old film tradition"!
I would comment that
(a) if it's a tradition, then watch the bloody film with your own son like you did when he was a child - the "tradition" is "watch with mummy" not with granny.
(b) I would not want a child set in front of a screen for 90 minutes at that age!

I swear most of the moms who post on here sound exactly like that.

My 6 month old wouldn't even watch the tidler on bbc1 for 20 minutes so I'm not sure how she thinks your DD will watch a whole move. It seems like she likes to be in control.... well, you are the mother now and she, the grandma and you are making your own traditions. Doesn't like it, go home.

My DM can be like that.

For example, she and other family members were treated to a meal out by me and my DP. She bought a round of drinks and somehow squeezed more thanks and appreciation out of that "let me pay my way" gesture than I did for footing a massive restaurant bill!

If my MIL wanted to take my child for the afternoon I would happily accept it and use that time wisely. We have had zero offers from our parents over the years so I'd make the most of it.

I would not have expected a financial contribution for the dinner, so I'd be grateful for that too (I think, for a lot of people, it wouldn't even occur to them to offer). Actually, to be honest, I think I'd refuse it.

I do appreciate that she's showboating though. I have an aunt a bit like this - laying down the law and this is how it's going to be. Not in a nasty way, but just likes to show you that she's in charge and this is how she wants it. Seems to be a lack of self awareness. I can see how this would be irritating from the MIL if you're confined to days of it together. All the more reason to take her up on her offer and give yourself a break. It does sound a bit like cabin fever - cooped up together and personalities clashing.

Yep.
Besides, a 6 month old baby doesn't watch films. And MIL doesn't need to be alone with her to watch a film. By demanding to have her alone, she's exerting dominance over you. Taking your baby off you for her own stupid reasons is showing you that she's as important in your baby's life than you, her mum. She's doing it for herself, not to benefit the baby.

Also, something a person has just decided to do isn't a tradition. She's ridiculous.

She's an attention seeker and wants to be the most important person in the family. And your husband is making it worse by pandering to her. He shouldn't be going behind your back to agree to his mother's absurd private film-watching session with your baby. Be careful, he's likely to continue undermining you if he wants to pander to his mummy.

She's insisting on being alone with baby? Why is that so very important? It's creepy. For some phony tradition. What an odd woman. I wouldn't let they even get off the ground at all ever.

There's some odd people about.
Self important waffle - I love Christmas but if I pulled half the crap some of these parents pulled on their adult children and their families, I wouldn't get invited anywhere.
Tell them to get a life .... do they any other friends?
Is that why they try and control the narrative to feel some sort of self import control.
They need a hobby.

I have a MIL like this, which is why we don’t see them at Christmas any more.

she used to insist on giving us £100 in saving stamps for a supermarket that wasn’t near us, when she knew we always do our food shop online, you could only use the stamps instore in between certain dates so it was inconvenient to have to drive quite far to a supermarket we don’t usually go to at the busiest time of the year, we used to just use them to stock up on booze for the year. She would then tell anyone who’d listen that she ‘always pays for our Christmas dinner’ and we’d have to be ever so grateful or she’d sulk. As soon as we moved to a town closer to the supermarket she stopped giving us the stamps, when they probably would be more useful now 🙄

I think I would start laughing if my MIL started clinking a glass to make a speech when you are having a perfectly ordinary Christmas dinner.

I agree with whoever said this is a DH problem, he's scared of his mum and ends up pandering to her silliness. I think in an ideal world, you would cut her some slack and he would step in if it was becoming inappropriate or putting more work on you.

I would have difficulty keeping a straight face and not taking the piss though, I mean watching a film with a 6 month old, they can hardly focus on the screen!

Why do people think they have to to tie around PILs? It's your house. It's your child. Frankly I'd be happy if she wanted to take my baby off my hands for a couple hours - I'd take the opportunity to run a nice bath or read a book or take a nap!
But you don't have to take it - when she goes on about transferring the money say 'thanks but you haven't done it yet, do you need my bank details'? And don't keep thanking her - once is enough (after all is she thanking you repeatedly for having her to stay? For cooking and cleaning constantly)? If she says it will be an annual tradition just say 'we have no idea what we are doing next year and might go away'. Say it's a tradition you want to start with your family.
If she wants to make a speech then fine but just smile and nod and switch the topic when she's done. The speech should be thanking you and her son for giving them such a nice Christmas!

And she's trying to establish HER traditions in someone else's house?!!
Cheeky, presumptuous mare.

My sister is like this. She is very insecure and does this to "seek a connection". It is just a form of seeking validation when she has very little self worth. It is like she is desperately frightened if it isn't tradition then she will be left out or forgotten next year. In an ideal world she would acknowledge this and work on herself. However this will never happen and I just tolerate it by seeing the reason behind it and empathising with that.

I am not sure about your MIL but my sister (who is twelve years older) had a difficult childhood and really threw herself into the role of trying to make everything perfect for us as children. She thinks that she "sees" where something special is needed, because I think she desperately wanted to be seen back then.

I agree it is absolutely as annoying as heck. I just try to put my foot down when it verges into age inappropriate behaviour (like movies that are way above my kids understanding, or going to 'special' restaurants that don't cater for my kids), or when it turns into emotional labour for me and my little family. However most of the time I just remember not everyone's perfect and don't emotionally engage or get caught in the trap.

Just say thanks here are our bank details and end the convo about the money. How long can the chat about it be?!

With the film that’s clearly crazy. Where are you going to go if she’s watching the tv? And insisting on being alone. Maybe your child will be asleep then

I would do my best to get DD to be asleep when the appointed time for the film viewing came round.

I think it’s time you need to be ‘upset’ and stop half this nonsense.
It’s emotional blackmail!

You have a DH problem not a MIL problem.

It obviously costs more than £100 to host 2 people, one of whom likes a drink, for a week over Christmas. Why has he not told his parents this? Or at least joked 'thanks Mum, that'll cover 1 turkey leg and Dad's wine for today'

The film - why can't he tell his mum she's ridiculous and babies don't watch films? His biggest issue was that you had upset his mum.

He needs to step up fast about how there will not be a tradition of them staying a week every Christmas, £100 barely touched the sides and she is upsetting his wife.

I couldn't bear this, but then I'm so introverted/ asocial that I took myself off for a bit, several times today... it was just me, DH, our two teens and one other relative. A week with someone like this would be WAY too long, and I'd have snapped something PA about not being a traditional type of family by about day 2! Fuck her weird, made-up 'traditions'.

(So glad my kids were a bit too old for the new 'traditions' of elves and Christmas Eve boxes too! And I won't wear or buy Christmas jumpers... bah humbug! Nah, I love Christmas - just hate being told what to do, wear and buy!)

So if she wants to make it a big thing all the time, why not try doing the opposite and totally downplaying what she does. So when she offers money, reply 'oh don't worry Margaret, it's such a token amount it's hardly worth bothering about'.

As for the film, say 'oh you're welcome to watch any film you want, Margaret, but DD is 6 months old, she doesn't watch telly.'

I couldn’t listen to it. I wouldn’t have them stay for a week anyway that’s for sure

It's attention seeking and sounds like her family have pandered to it. I wouldn't join in if I were you - just say 'yes, that's great thank you' when she offers the money and I would have laughed when she said she wanted to watch a film with a 6 mo old baby!

God this sounds such hard work, and all the more because what can you really say...? And yet it is really annoying and joy-sucking. A bit like watching two small children have a brief funny interaction and enjoying that, but then somebody goes on about how they are now best friends, or girlfriend/boyfriend, and never shuts up about it, and the brief sparkly moment becomes this big heavy adult crap.

I think I'd be gritting my teeth so hard I'd risk cracking a molar. The best option i can think of is to just to react as little as possible and never mention these supposed 'traditions'.