p2 – bypassing wp-admin when logging in

I’ve set up p2 on this domain https://tshirtalert.com/wall/. Basically, I want anyone to be able to register to this blog, and make updates through the P2 front-end, rather than through the WP-Admin panel.

In fact, I want to bypass the WP-Admin panel completely for everyone except the site Admin (which is, of course, me!). So whenever anyone logs in to this blog (using either the Login form widget in the sidebar, or using the login form on the url: tshirtalert.com/wall/wp-admin), I would like this user to be re-directed straight to the homepage, rather than to the WP-Admin panel.

How do I achieve this?