I made the mistake of giving my Whatsapp details to some clients when I was doing a job in India, now I'm basically on call all the effin time. Even after leaving the company.
In one band we use a single Whatsapp group, a Dropbox, and emails where necessary. In another we use Whatsapp and a german language online app called Teamplanbuch. It's a team project tracking tool, there's a row for each band member, then columns for each important upcoming date - practices, gigs, etc, screenshot attached. Everyone goes through and populates it in advance, inserting holidays, days when unavailable, you can add comments to each entry. BL decides whether or not to cancel or shift practices based on the inputs, and the app sends email reminders to everyone. It's Swiss level band organisation, and it works pretty well. Not suggesting this app, as I think it's only available in German, but I'm sure there are other programs offering that type of thing.