Appel ID: How do I sepearate for msgs but keep same purchases across devices?

I have multiple iPhone and iPads in my house for various family members

at times messages sent to me make their way to other devices.

I would like to:

•Prevent these devices from getting my messages

• Allow these devices to text with their own accounts
(I tried using a gmail account but the devices will not relinquish my @me or @icloud accounts)

• Allow the devices to share one time and ongoing service purchase I pay for though my account.

I currently have one apple Id and one @me.com and one @icloud.com account