I followed Mama's advice and it seemed to work. If anyone else is having the same email problem, these are the same steps I followed:
- From the iCloud website I unsubscribed from all shared calendars on my Mac
- From the iCloud website I unsubscribed from all shared calendars on my wife's Mac
- From the iCloud website I sent invitations from my calendar to my wife's iCloud account
- From the iCloud website I sent invitations from my wife's calendar to my iCloud account
- I then received email notifications of each shared calendar, clicked on that link and subscribed
- After subscribing there was a check box to opt in to email notices. I left that unchecked.
Notable differences from my previous attempts:
- I did everything from the iCloud site rather from the iCal app
- I had both Macs in the same room so I could send and subscribe to the various calendars quickly
I tested a few new calendar entries and deleted a few and it seemed to work OK.
No more emails - YEAH!