Child pages on parent page problem

Hi all,

So basically I need to display child page excerpt, thumbnail and title by category on the parent page. I have everything working, however, it shows all pages in category and not just those pages that are sub or child pages to the parent page. This code would be in a page template and so would work for multiple pages.

Please offer any advice you can think off and I will try it, I have been racking my brain!

Thanks again, the code is below:

<?php if ( have_posts() ) {  /* Query and display the parent. */
	while ( have_posts() ) {
	the_post();
	$thispage=$post->ID;
	}
} ?>
<php? /* Back up global $post object. */
$post_backup = $post; ?><div style="width: 100% !important; float:left;">
<div class="comparison-stories"><div id="comparison-container_division">
<?php $childpages = query_posts('post_per_page=5&orderby=menu_order&order=asc&post_type=page&post_parent=.$thispage&cat=16');
	if($childpages){ /* display the children content  */
	       	foreach ($childpages as $post) :
	        setup_postdata($post); ?>
 <div class="comparison-post-block"><div class="wrapper"><div class="top-5-image">
<?php the_post_thumbnail('medium'); ?></div></div>
<div class="comparison-top5-text">
	        <div class="wrapper"><div class="top-5-title"><p><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></p> </div></div>
		<div class="wrapper"><div class="comparison-content"><div class="comparisonexcerpttext"><?php the_excerpt(); ?></div></div></div></div></div>

	 <?php
	  endforeach;
	 } ?>
<php? /* Restore global $post object. */ $post = $post_backup; ?>
</div></div></div>