MyChildPostClass.php

<?php

  function MyChildPostClass extends TimberPost {
  
    function special_children() {
	/* modify the query on line 7 as you need */
	$children = get_children('post_parent=' . $this->ID . '&post_type=post&numberposts=-1&orderby=menu_order title&order=ASC&post_status=publish');
	foreach ( $children as &$child ) {
		$child = new $childPostClass($child->ID);
	}
	$children = array_values($children);
	return $children; 
    }