JohnHair.com

Can my wife and I share our mycal pros on our Apple 4s phones?

Yes this is certainly possible, however you will need to use the standard Calendar app on your device to create the share.
To do this:

Go into the standard Calendar app
Tap Calendars
Tap the calendar you want to share
Enter the email address of the person you want to share your calendar with

That should be all you need to do. You can go back and modify the share, for example you can set if the other person can make changes to the calendar, or can only view it.

Let me know how you get on!

Regards
John

John:
Did what you described.
Current status:
My phone: In the Calendar app under "edit calendars", the iCloud account says, Home calendar " shared with my wife.Then further on the next window I allowed her to make changes on the calendar.
So far, nothing has appeared on my wife's phone. Incidentally . I also purchased my Cal Pro for her phone, not knowing whether that was necessary or not.

Ok over the weekend I set up a test iCloud calendar on my phone and went through the same share options you have done and shared with another iCloud user.
They received an email from noreply@insideicloud.icloud.com which contained the invitation. Click on the Join Calendar link on their iPhone added the shared calendar and it was visible from myCal PRO. We can then both add and edit events and they appear on each others device within a minute or so (when connected over wifi).

I would suggest removing your wife from the shared list in that calendar and trying again. Best to make sure you share with your wife's iCloud account email address.

Let me know how you get on!

Regards
John