Where you have the call:
isAuthorized("",$MM_authorizedUsers, ...
you have $MM_authorizedUsers as a comma separated list containing both 1 and 2.
If you were to call it with just one of those values then you can put code that is specific to people who have that level of access into an if statement that does that call.
Code:
if (!((isset($_SESSION['MM_Username'])) && (isAuthorized("",'2', $_SESSION['MM_Username'], $_SESSION['MM_UserGroup'])))) {
header("Location: dashboard2.php );
exit;
}