Am I unreasonable or is MIL

YANBU. It’s just a basic fact that you don’t make plans for other people’s children without checking with their parents first.

I agree with some PPs that potentially awkward discussions are safer had in person than by text, but her response was absolutely outrageous. Even if tone is hard to read by text there is no justification for her behaving like that.

I would query whether she’s a safe and reliable person to provide childcare. She didn’t ask your permission before making a plan for your child and she clearly cannot accept rules or limitations. Further incidents of this kind will occur. If you have alternatives available I would try and move away from this arrangement and she can see your son when you’re all together or in contained circumstances in future.

She should have checked with you before making supper plans, your text to her was rude and sounded as if it was telling her off.

Stop using her for childcare.

If my MIL had said that I would have said 'That's great. Thanks. He can spend some time with cousin'. However, in future have a full proof excuse to stop it from happening again. 'Sorry, MIL, but son must do his homework and have a snack when he gets home. Perhaps in the holidays would be nice'. She is doing you a favour and there is no way I would look after my grandchildren on a regular basis. I've done my bit and would see them from time to time.

Good grief🤯

Same, they would be the last time she ever looked after him. Refusing to give him back and telling you to come back later - wtf? You’ve been very measured.

WTF? This is a bizarre reaction to a perfectly reasonable thread. Much like the MILs reaction to the text!

OP, as others have said, texting wasn't the way to go but in the absence of a backstory, your request was reasonable and she should have checked with you first before arranging things, outside of the normal childcare, with you

Always better to have these as actual conversations in person rather than by text message.

Weirdest part of this story for me: why weren’t you invited to dinner with MIL, SIL and the kids as you were there and had to come back anyway.

To answer the actual question, MIL should have asked you before making arrangements. She was very rude to assume a change of plans would be ok and then not even inform you to save you a wasted journey. She knows she fucked up, that’s why flew of the handle and started making up random accusations that had nothing to do with this situation.

Pay for childcare op.

Sorted.

This wouldnt have bothered me but I have a great relationship with my MIL and love her like my own Mum. I wouldn't have sent a text like that to her either as it sounds patronising. But every relationship is different and only you know your relationship with her.

She should've checked with you. He is your child not hers. Free childcare or not, she doesn't get to dictate when you can take him home. She also should not have told him what her plans were.

I disagree with others. A phone call possibly would've been better but if she was like that over text, there's potential she would've flipped if OP did it face to face too. In front of the child.

I would look at paid childcare from now on.

You sound like the MIL

She sounds mentally ill.

I wouldn't be letting her look after a child if she is that explosive and unstable.

YANBU what a rude woman.

This is a good response.

OP, you need to find paid childcare. Your mil does not have first dibs on your child, you and his dad do.

And in case it needs saying again, find paid, professional childcare.

So you’re completely right and she’s completely wrong. That’s it isn’t it op? That’s what you want everyone to say to ease your conscience? The fact is you use her for free child care but only begrudgingly and on your terms and you were pissed off that your son was looking forward to something she’d organised. You didn’t need to send that text but you did because you do hate her and you wanted her to be upset as you. YABU.

She should have called you during the day to ask whether her plans for your DS in the evening would be OK. That should have been done before she promised DS anything, just in case it wasn't OK.

You should also have reacted more forcefully when she told you that you couldn't take your own child home. He is YOUR child, not hers even though she has provided some free childcare.

Personally, I would have insisted immediately that my child would be coming with me. To her face, not by text later on.

You may need to source different childcare.

My MIL went CRAZY in response to this message, “how dare i disrespect her like that, how dare I, she always does her best for the children, she always knew i hated her, im upsetting everyone, making her husband ill”

This didn't happen over a polite text.

There's something going on and if there's no backstory and you've both always got on wonderfully, I'm surprised you're not worried about her?

I wonder if her extreme overreaction is because she doesn't like boundaries - this making plans for your DS after the time you always pick him up is a massive overstep - and she doesn't appear to like being called out on it. Does everyone always cater to her? Might explain the making her husband ill comment.

Paid childcare doesn't cause these issues.

Clearly your MIL harbours resentment for whatever reason and you need to make alternative arrangements for your child.

Texting isn't a good way to communicate something sensitive but her response was ridiculous.

Well, you both have behaved badly. She shouldn’t have arranged something without checking with you, you shouldn’t have tricky conversations by text - you do it in person, and she shouldn’t have gone batshit when you did.

So you both need to apologise. If you want the free childcare, I’d go first.

Yanbu.

She should have told you beforehand that she had made evening plans as that way you could have cancelled your own plans and saved a wasted journey.

It's basic manners.

What were your own plans?