How to best sync multiple collections of contacts between multiple users

What is the best way to sync multiple collections of contacts among multiple users on iOS and OS X?

For example, suppose I have three collections of contacts: Bob's, Sally's, and Common. I want Bob to be able to access and sync Bob's contacts and Common contacts, and Sally to access and sync Sally's contacts and Common contacts. Bob and Sally never need to access or sync each other's contacts. Bob and Sally would both sync and share contacts in Common.

How would I best implement this? It's my understanding I have three options for managing contacts across iOS and OS X: 1. iCloud accounts, 2. Install OS X server, or 3. Install and manage Darwin CardDAV directly. Which method would best support what I wish to do?

I am a seasoned Unix geek well versed in the terminal, so I am prepared to get my hands dirty as much as necessary to achieve what I want. Also, it is sufficient if syncing takes place over WiFi on the local network, in fact, that is desirable versus syncing over the cloud.