To think you don’t do someone a favour and then charge them?

I agree with OP. Clearly one doesn’t ask “do I owe you anything” if your child has gone round to someone’s house for a “play date “. However if someone has had your child for the day, even if it’s their best friend and the mother has offered, it is a very normal question. HOWEVER it’s sort of rhetorical; it’s an unwritten rule that the correct response is “of course not, my pleasure” and will usually mean that at best your child has been treated to a happy meal and that at some point it will be reciprocated.
If there were plans to go to build a bear and have an expensive meal then OP should have been warned in advance.

I’d return the build a bear teddy to the friend and pay for the other costs.

You don’t incur costs on a £40 teddy (which I wouldn’t waste money on even for my child’s birthday) without getting permission first from the person you expect to pay!

Asking “how much do I owe you?” is not a normal question to ask in this scenario, so I suspect you’re not telling us the full story. There must have been some discussion about her doing an activity with the children to prompt you to say that. If you really thought they were going to the park and eating at home, you wouldn’t have asked that question.

Clearly they did go to Build-a-Bear and your DD probably loves her new bear, so you’re just going to have to suck it up. You got a day’s childcare, your DD was entertained, fed and looked after, so £70 is reasonable for all that. Pay up and move on.

I'd just give the £70 to friend to pass on

This I'm afraid. Like you literally asked her so just pay her.

A days child care at £70 - not too shoddy

It wasn’t a platitude if the OP was trying to cover the cost of her child’s lunch, soft play etc; she just didn’t expect the bear.

I wish people would use their language appropriately and say what they mean. It would be so much easier that way. For example - my DP is a CF who does not propose marriage and gets all the benefits of a wife without offering her any financial protection. Or 'we should have a coffee at some point' means 'I don't want to ever see you again'. Or in this instance - 'how much do I owe you, give me your bank details' means exactly that. Say what you mean and mean what you say and life will be wonderful.

I would ask and expect to pay for lunch, a coffee and bus fares. I wouldn't imagine people spending money on expensive toys.
People do really weird things tbh.

I've had to vote YABU purely because you asked how much you owed her, if you're not going to pay then why would you ask?

If she'd spent that much without asking you, THEN asked you to pay without you offering, she would definitely be the unreasonable one! And you would have had the perfect get-out clause, and could have told her you hadn't budgeted for that and couldn't afford it (especially with the costs of having to travel into London), and she should have checked with you first.

But - you asked how much you owed!

The danger of using platitudes. One day someone will call your bluff.

Build a Bear is so expensive. I remember being fleeced when I took dd and that was the bear, little outfit, the voice box etc. It all mounts up and before you know it you're paying a fortune. I remember paying about £80 and that was 10 years ago. I imagine she took the girls out to town, got dragged in there by them and before she knew it had paid a fortune. You did ask how much you owed her. She's probably hoping that she'll recoup some of the loss. Sounds like the day cost her a fortune. Eating out with 2 kids isn't cheap either!

As a generally British and polite sentence filler, I said ‘How much do I owe you?’

That's not a sentence filler or a British tradition. You've paid the Wet Lettuce Tax.

It’s super odd to take a child on an expensive day out without being clear that the parent is meant to pay. If my kids go to soft play or whatever with friends it’s a plan - they say they’re doing whatever, I say if that’s okay. Then I pay for my own kid. Or I say no thank you and we meet up another time. I would never spend that kind of money on a toy!

But you already offered to pay and you did need the favour so unless it’s a huge financial issue I’d just pay - or tell them it’s too much and give the bear back?

I might have said “Do I owe you anything?”, particularly as it wasn’t actually my friend who was dong the favour. But I would have expected the answer “Oh no, that’s fine!” Certainly not “70 quid, please!” And if I had chosen to do something expensive with someone else’s child I would certainly expect to pay for it myself. And if anyone does “judge” you for the arrangements you made, they are idiots.

I’d have asked too. Quite normal where I live.

but I’d have been annoyed at the presumption of taken them to an expensive rip off like build a bear.

Either grandma is loaded and thinks nothing of spunking £50 on Build a Bear. Or she’s skint and got a surprise at the checkout, hence wanting to be reimbursed.

Poor communication all round.

I’d pay it but mention it to friend, along the lines of “Bloody hell! Those bears are a rip off!”

Oh I know. I’ve only ever been once in my life and that was maybe 5 years ago. Came away with 2 bears fully clothed and shoes and £80 lighter. Never been back since. Can only imagine how much they have gone up with inflation

You asked, therefore you would be unreasonable not to pay. I expect grandma spoiled them and then regretted spending so much, you gave her an out.

Did you ask how much you owed after she'd told you about the activities?

I can imagine offering to pay for those as part of the chat when collecting your daughter but I'd find asking how much you owe before that - so clearly meaning her time - is actually really awkward and a bit rude!

I would expect to pay £40 for lunch and a few £ for bus fares. Not an expensive toy.

@Gymmum82 I mean a fully dressed build a bear is probably about £40 if not more.

😮😮 Totally OT but that's just given me a fit of the vapours! Admittedly it's been years since I was last in BAB but 40 quid is crazy money.

I think you should pay purely because you asked how much you owe her. It's also cheeky to go somewhere expensive if you're doing someone a favour and hoping they will pay you back. So two lessons learned here: don't use them for favours anymore, and don't ask someone doing you a favour how much you owe them!

Well this is quite the crazy tale. Some might even call it unbelievable!

It's an expensive lesson. I'd wager the grandmother didn't want to do it and was convinced by her daughter.