My parents were very strict and moody when I was growing up. I never knew whether I'd get home from school to hugs or a telling off. They're still very moody and uptight now but in general are pretty good with my kids and seem to enjoy spending time with them. I never ask them to have the DCs, they always ask to have them.
Occasionally, despite asking to have them, my 2 DDs (DS never stays as he's too little) will come home and say that Nan and/or grandad has been in a bad mood the whole time they've been there. Yesterday they asked to have both girls overnight (aged 12 and 6). The girls stayed and were dropped off this morning. When my mum had gone, DD1 said that my dad shouted and shouted at her last night for not getting ready for bed quickly enough, and made her cry, then she was sent to bed where she cried for ages. Okay, she does dawdle sometimes but I don't think it warrants an enormous bollocking, especially as it's meant to be fun staying with grandparents and they'd asked to have her. Then this morning she said my dad started shouting at her again about it all and made her cry. DD2 said she was drinking milk when my dad started shouting and it made her jump so she spilt a bit of milk on the table and then my mum shouted at her.
Clearly there was something on my parents' minds to make them in a bad mood like this but AIBU in thinking they're wrong to shout and make my girls cry when they hadn't actually done anything wrong. Both have said they don't want to go anymore as "Nan and Grandad make up things we've done wrong and tell us off". They did the same with me as a child too BTW, bollocked me for nothing...