Who IBU in this scenario?
Dcs age 5 and 8 have a half sister, nearly 17, who they live with with their mum. The smalls stay 2 nights every week at their Dads.
The dad has a new job and didn't take into account childcare for his first day which was on the Monday of half term so asked their older half sister to look after them for him. It was her only 'day off' that week.
He offered to 'buy you guys lunch' and wanted her to look after them 11-2.
The sister and the grandmother (who drove) took them to a soft play area and bought lunch which came to £39 in total.
Their mum was working nights so couldn't have them.
He originally gave the sister £10 in cash which paid their entry into the play area.
He came home 2.30pm.
He asked how much it had cost and she said £30 ish. Then he said "let me know how much your food cost and message me".
Later he messaged the GM to see what it all cost but she wasn't sure as she hadn't paid any of it.
Then he PayPal'd the mother £15 to give to sister with a message that he didn't feel it was reasonable and they were taking advantage of him by taking the kids out and expecting him to pay.
Sister didn't ask for any money but kind of expected it as he had offered to pay for lunch.
The Dad earns nearly a 6 figure salary just to be clear.
So who IBU?
The sister for assuming the smalls' Dad would remunerate her for the cost of outing or the Dad for not covering the costs of the outing or paying the sister for babysitting.