Assistance with child pages

Hi

I am trying to create a small listing pages using child pages.
Example
top level page shows its child pages to one level
each sub page shows its child pages to one level

I have acheived this using

<?php $children = wp_list_pages('depth=1&title_li=&child_of='.$post->ID.'&echo=0');
  if ($children) { ?>
  <ul>
  <?php echo $children; ?>
  </ul>
  <?php } ?>

What I would like to do is show a brief description of what each sub page is about and a small thumbnail.

So it would list each sub page to one level and below the page title link have a thumbnail image and a short description.

Could anyone point me in the right direction