You can setup a "dummy" google account just for use in the car, set-up two dummy accounts if you and wife want to personalize the seat/mirror position, car settings, and app selection (spotify, youtube music, etc.) for each of you. You wouldn't be able to use any messaging apps integrated with your car, but you would still be able to link your phones via bluetooth.

I've setup dummy google accounts so I can use old phones as a GPS device on my bike & motorcycle, no worries than if the phone is lost, stolen, broken, etc.

 

You might also wait a little longer for Apple Car Play to become available. Are your mobile devices Apple or Android?

 

What is the issue with linking Google account? You can always create a separate account just for car but will miss out on sync with your phone.

 

My wife and I have been driving our P8 for over a year without adding personal Google accounts—driver profiles and memory settings work fine. I setup our key profiles and remember reading that a Google account was optional.

For music and phone calls, we just use Bluetooth and never allow contacts to sync to the car. I don’t like to make calls while driving, but in a pinch will use Hey Siri (directly from the phone) to dial a contact or send a text.