My SIL has three kids and is a single parent.
She works in the NHS as a nurse. She works three days a week. She works in ITU.
She could send all three of her kids to school that is five minutes down the road as she a key worker but instead is driving them to grandparents three days a week and they are having them. She is then staying for tea every night when she gets back.
My FIL is 72 and my MIL 69. They have both had medical issues in the past but nothing too serious. My FIL is a type 2 diabetic which is dangerous with this virus but maybe not as dangerous as type 1
Not sure if she is doing the right thing but leaning towards she should be sending them to school and leaving grandparents alone. Also if they are looking after the kids surely it should be a quick drop off and pick up.