thanks @elliot but I think that just gets me back to my original question of how to limit that query, say to just return 3 posts (bonus points for returning random posts). It seems by default it just returns all the posts in the relationship.
I’m basically looking for the equivalent of:
<?php $query = new WP_Query(array(
'posts_per_page' => 3,
'orderby' => 'rand',
));
?>