My gut reaction is that this wouldn't be allowed or okay, so I'm not going to give a really detailed scenario, but just asking for others' instinctive reactions also.
Say one parent is non-Corona ill and likely to be in hospital for periods, and it would be almost impossible for the other parent to look after the children at home at the same time. The grandparents (who live in another town and are in good health, not in vulnerable groups and so on) are happy to have the children to stay for a few weeks. Could this be acceptable?
Yes - it is okay, to save the kids from a distressing situation and the parent from wearing themselvea to a frazzle
No - because, just no.