$args = array(
                'post_parent' => $post->ID,
                'post_type'   => 'page',
                'post_status' => 'any'
            );
$children = get_posts( $args );
// $children = get_children( $args ); //this also works,btw

foreach($children as $child){
    setup_postdata( $child );
    echo "<h1>" .  $child->post_title . "</h1>";
}

$args = array(
                'post_parent' => $post->ID,
                'post_type'   => 'page',
                // 'numberposts' => -1,
                'post_status' => 'any'
            );
$child_pages_query= new WP_Query(args);
// echo $child_pages_query->post_count; // wrong answer already!
if ($child_pages_query->have_posts()){
    while($child_pages_query->have_posts()){
        $child_pages_query->the_post();
        echo "<h1> " . $post->post_title . " </h1>";
        }
}