@gremlins I'm sorry you had to add that edit!
Our experience:
It's close to impossible to protect the children at school (because of the teachers). The children wear masks in public transport, shops, theatre, etc., but not at school 😠
So our focus is to prevent spreading diseases between household members. We have a built-in ventilation system that is always running on low. When someone has a "cold", it's on high. Also whenever someone else is here (like maintenance), and especially when grandparents (who are the people who need to be protected most in this setting) visit, it's on high. We don't get a lot of visitors.
Otherwise, "normal" hygienic precautions, like washing hands when coming home, before eating, after bathroom. Everybody uses their own cutlery, toothbrush, towel, etc. Keep tissues in a closed container and remove asap (I don''t know how much of this is "normal")
Like this, we've not had infections passed between the kids or from kids to parents.
Oh and, we eat at restaurants practically only in the warm season when we can sit outside. Otherwise only very, very rarely, and with nasal spray and a mobile air filter on the table.
We have the maximum vaccinations that we can get here, which is influenza and covid both yearly. Try to convince the grandparents, but only one side gets them. (Influenza might kill one of them, but at least they won't get it from us...)