WordPress Child Pages’ Featured Image Descriptio

I’m using this code to display child pages’ features images;

<?
$child_pages = $wpdb->get_results("SELECT * FROM $wpdb->posts WHERE post_parent = ".$post->ID." AND post_type = 'page' ORDER BY menu_order", 'OBJECT');

if ( $child_pages ) :
foreach ( $child_pages as $pageChild ) :
    setup_postdata( $pageChild );
    $thumbnail = get_the_post_thumbnail($pageChild->ID, 'thumbnail');
    if($thumbnail == "") continue; // Skip pages without a thumbnail
?>
    <div class="child-thumb">
      <a href="<?= get_permalink($pageChild->ID) ?>" rel="bookmark" title="<?=     $pageChild->post_title ?>">
        <?= $pageChild->post_title ?><br /><?= $thumbnail ?>
      </a>
    </div>
<?
endforeach;
endif;
?>

And I’d like to display the featured images’ descriptions on the parent page as well.

FYI, this is the web page;

http://storyville.jonmarkoff.com/storyvillewp/our-work/

Thanks!