How do we sync contacts and calendars (ONLY) between two iCloud accounts, two iPhones and one iMac with two user accounts?

Question

This is complex.  Until today we had one iMac with two user accounts - one for me and the other for my wife.  We sync'd our calendars and contacts between our two user accounts using my iCloud account, thereby keeping our schedules coordinated and our contacts information always the same between us.  Also, as I had an iPhone, I sync'd my phone with my iCloud account, thereby keeping the contacts and calendars in the two user accounts on the iMac AND my iPhone sync'd.  (I also sync'd other things, like Notes and Mail and Safari settings, between my iPhone and my user account on the iMac, but my wife did not want to be burdened with all my emails showing up in her email account and I wasn't interested in hers, etc., so we didn't sync anything between us other than calendars and contacts.)
We've finally bought my wife an iPhone and set up an iCloud account for her.  And of course she now wants to sync several items from HER account on our iMac to HER iPhone, but I don't want them, just as she doesn't want all of my other stuff.  But we still want our mutual calendars and contacts to sync to HER new iPhone, just like they already do to mine.  But I can't figure out how to CHANGE her iMac user account from using MY iCloud account on the iMac to using HER new iCloud account, and then having HER iCloud account speak to MY iCloud account but share JUST our calendars and contacts.
Originally I tried a workaround by simply having her iPhone log into my iCloud account.  That works great for the calendars and the contacts.  But...she can't sync anything else from her iMac account to her new iPhone because she's presently "forced" to use my iCloud account.  And neither of us want to sync our other things to each other's iMac accounts or iPhones.  Also as we're both using my iCloud account, in things like the Find My iPhone app, the Cloud is seeking two phones labeled with my name and none with her's.  So we definitely don't want this as the set-up and communications network between our devices.
We want to set up our users on the iMac to sync to our SEPARATE AND DIFFERENT iCloud accounts and then have those iCloud accounts sync calendars and contacts (ONLY) between themselves, and then push that data to our separate iPhones (or the other way, from either of our iPhones to the individual accounts on our iMac and the other person's iPhone).  Does this description make sense to you?  I've diagramed it nicely using Keynote, but even thiough I can draw it, I can't figure out how to set up and configure all the devices to make it work.  If you would like me to send the Keynote slides (just two of them - the current and desired configurations - please send your email address to me at [email protected] and I'll be happy to forward it to you.
If anyone can help me set this up I'd be most appreciative!  Thanks so much.  Merry Christmas and Happy New Year to all readers in this community!

Answer 1

BobT.
I had the same problem, and decided to look into it last night.
First of all, the solution I would like to have is for Apple to allow for selection of iCloud accounts per application, i.e. Contacts to one, Photo Stream to another. I believe this would be the most straight forward solution for the problem we are facing. 
Since this is not an option I came up with a workaround. I was most interested in solving this for Contacts, so this is what I tested for. Now I have all 3 devices with the same contacts.
1) Turn off iCloud for Contacts on all devices. On the device that has the Contacts list that you would like to propagate to all others select to keep the contacts, and on the others select not to keep them.
   Note that the current backups still exist on iCloud, so in case something goes wrong you can still turn the iCloud for Contacts back on to get your current Contacts back.
2) In iTunes, sync All Contacts with the phones, starting with the one with the Contacts content you chose to keep.
From this point on, the 3 devices should sync contacts with each other.
This, of course, will stop your iCloud backups of Contacts, but I don't think this is really needed. You are already storing copies of your Conacts on 3 devices, which for good parts of the day are likely not all co-located. You also potentially have Time Machine backups turned on, which would mean there is a 4th copy there as well. For the case of Contacts iCloud only complicates matter ... that is until Apple implements the solution I first wrote about.