You need to register/enqueue your admin scripts on admin_enqueue_scripts, not on wp_enqueue_scripts. wp_enqueue_scripts is a front end hook. It won’t run on the admin pages.

Secondly, is_admin() just checks whether the page is an admin page, not whether the user is an administrator. To check whether the user is an administrator use:

$current_user = wp_get_current_user();
if (user_can( $current_user, 'administrator' )) {
  // user is an admin
}

Reference:

http://codex.wordpress.org/Function_Reference/user_can
http://codex.wordpress.org/Function_Reference/wp_get_current_user