Separate everyone's phones & our Mac from receiving everyone's texts while sharing the same account?
The apple ID is the user.  At some point you'll need to bite the bullet and create new apple IDs for each user if you want separate texts/email accounts etc.

My wife and I use a multitude of applications that can share data across accounts, like


Anylist for reminders/grocery lists, etc (this can be integrated with the Reminders app
Photostream for photos
Google Docs for notes


Also, since iOS 8 you've been able to share applications purchased on any apple ID as long as they have the same credit card on file - so if my wife buys an application, I can download it for free, and vice versa.  It's unfortunate that they still don't support sharing app data, but maybe that's in the works.  Regardless, you will continue to run into problems down the road if you don't separate out your accounts with new Apple IDs.