cat and child cat posts

<?php
    $parentCatName = single_cat_title('',false);
    $parentCatID = get_cat_ID($parentCatName);
$top_cat = get_category($parentCatID);
    $childCats = get_categories( 'child_of='.$parentCatID );
$childCats = array_merge(array($top_cat), $childCats);
    if(is_array($childCats)):
    foreach($childCats as $child){ ?>
    <h2><?php echo $child->name; ?></h2>
    <?php query_posts('cat='.$child->term_id);
    while(have_posts()): the_post(); $do_not_duplicate = $post->ID; ?>
    <!-- POST CODE -->

    <!-- END POST CODE -->
    <?php
    endwhile;
    wp_reset_query();
    }
    endif;
    ?>