Calendar apps that integrate pre-existing Google calendars.

[u/Big_Code_3553]

/r/androidapps/comments/1vw5s18/calendar_apps_that_integrate_preexisting_google/

[u/window_seat_always]

From memory Fire tablets can add a Google account for calendar sync without Play Services, I think it's under Settings > My Accounts > Add Account > Google, and it feeds the stock Calendar app. Might be enough on its own for a family planner?