Unless you're going for more than five accounts, I'd put them on the same B.Net account.
That way, one authenticator is all you need.

Often, the game doesn't ask for my authenticator code.
But when it does, it will take you around 2.5 minutes to log in.

If you were to put them onto their own B.Net emails.
You would need an authenticator for each account.
And to remember which one was tied to each account.
You'd get into the game a little faster, when it calls for the authentication code.
But you'd miss out on Battle.Net bound items.