Private calendars are harder to deal with because you have to specify all the editors and viewers, whereas public calendars can be edited by any administrator (as well as any specified viewer). But you do avoid the issue of members subscribing to calendars before you're ready.
One issue to be aware of is that those involved in creating events would need visibility into all the calendars for maximum coordination. If, for example, you let only the RS leaders see the RS calendar and the Primary leaders see the Primary calendar, then when a Primary leader tries to schedule an event that conflicts with an RS event, the Primary leader will see only that it conflicts with a "Private Event."
Another point is that you can only reasonably use this approach your first time. Once you have an existing RS calendar with RS events, it's impractical to create a second private RS calendar for the new year. There's no way to merge the events scheduled at particular locations from a private calendar with an existing public calendar.
If you're calendaring far enough in the future, I've found that public calendars work just fine. In your situation, I think the complexity of trying to use private calendars is significant, and the benefits would be negligible. I'd recommend just using public calendars, so that those who are working with the calendars gain their experience in the environment they will be using going forward.
Questions that can benefit the larger community should be asked in a public forum, not a private message.
). To help orient the auxiliary leaders, I was thinking of starting with private calendars. Once events are entered and ready to publish, we would switch to "Entire Unit" visibility. Are there any issues/concerns with that approach?