Allowing logged in users to comment without moderation across a multisite installation

I currently do web admin for an internet community based on BuddyPress and Multi Site, and use the Comment author must have a previously approved comment setting to make it easier for users to comment and not be moderated. All users are vetted before their accounts are created so I know we don’t have spambots.

Initialize WordPress environment to use in a real cron script

I have to run a PHP script through real cron (WP cron being too unreliable). Within that script, I need $wpdb to insert data into WordPress table. But of course $wpdb will not be available as WordPress would not be initialized. Right? So, my question is how to ‘include’ WordPress/initialize WordPress environment to do such tasks? How about
require_once(“wp-load.php”)?