make my community private

I want to make my community a private membership
Community. When my members get to my site
They will have to use a username and password in
Order to see the content I provide for them.

At the same time I want to let the members create
Their own pages/blogs…similar to a family webstie
Where they can update family photos, child mildstones
Etc. Although they have to login to see my information
And to make changes to their site, I want to have their
Sites be public. So when they tell their friends to go to
Mysite.com/thejones…this page will be viewable in
The browser without the need of a password.

I will have the dolphin login page behind a password
Protected directory. When they login to dolphin it will
Also log them into the password protected directory.

So basically I want to have privat information that I only want my members to see when they login. But their own blogs and sites should be public
Is this possible to do?