S Planner
Just create a new gmail account for people you want to share calendars with. For example, I have a personal email address for my personal calendar, a work address that all my managers have the log in details to for a shared work calendar and another for me and my wife. whenever you add an event to the s planner just select which calendar (email address) to update and it will also sync with the other devices logged into this account.
How this makes sense!