from my own experience. There are some amazingly interesting use cases for organising family life. We have shared drop offs/pick ups with another family which is a constant flow of WhatsApp messages.

I too have thought of a shared comms channel for all "incoming family business" SMS & Email would be a good start, but WhatsApp is a non-negligible channel as well.

And dont get any parent started on the 35 different School/Club apps etc