May need some adjusting. This will get all direct children of $categoryID
of taxonomy type 'product_club'.
$args = array(
'child_of' => $categoryID,
'taxonomy' => 'product_club',
'hide_empty' => 0,
'hierarchical' => true,
'depth' => 1,
);
$cats = get_categories( $args );
The magic parameter is 'depth'.