wp-admin redirect and Activity + conflict

I'm developing a BuddyPress site and I don't want the members to have wp-admin dashboard access, but rather accomplish all of their content related tasks from the frontend. I am using the following function in my function.php file to redirect any curious members away from the /wp-admin url:

//blocks access to wp-admin for all except admin
function block_wp_admin_init() {

if (strpos(strtolower($_SERVER['REQUEST_URI']),'/wp-admin/') !== false) {

if ( !is_site_admin() ) {

wp_redirect( get_option('siteurl'), 302 );

}

}

}

add_action('init','block_wp_admin_init',0);

The problem is that the above function conflicts with Activity + and causes an error message whenever a member tries to upload a file. So, basically, my question is: can anyone point me in the right direction for preventing access to the wp-admin dashboard in a way that doesn't conflict with member uploads in Activity + ?

Thanks in advance!
-Alec