We sometimes have the little children over the road to play while their mum does the shopping/ has a rest etc. I know she is using me as free child care as DP loves to remind me but my dc love her children so I don't mind having them. This has been going on a couple of years now but they are no bother so it's all good. Their father works from home but I usually only see their mum.
She is currently pregnant and wanted to go with her DH to buy some baby stuff at the weekend so asked if we could have the children for the day.
I foolishly said yes and we had them for about 8 hours (much longer than expected). I tried to ring but they were 'stuck' in London. 
We ended up all going out for dinner in the evening so took them with us, dropped them home, all was well so I thought.
One of them left some bits at our house so I have just dropped them over and her DH answered the door and proceeded to tell me off for letting his children have ice-cream. I felt like saying well come back when you said you would. They never told me not to let them have ice-cream and it was only a small child's portion after their pizza dinner at a local Italian.
AIBU to be annoyed? I did them a favour imo and feel like I won't bother next time which is a shame as the children are lovely.
Sorry for the long post, thanks if you got to the end!