Limit the number of child pages

This is how I solved it:

<?php
 /*
  Template Name: home
  */
  get_header(); ?>

 <?php $counter = 1 ?>
 <div class="row-fluid"> 
 <?php
$args = array(
 'child_of' => 4,
 'parent' => 0,
 'post_type' => 'page',
 'post_status' => 'publish'
); 
 $childrens =   query_posts('showposts=3&post_parent=4&post_type=page&orderby=menu_order&order=DESC');

  foreach ( $childrens as $children ) :
 query_posts('showposts=3&post_parent=".$children->ID."&post_type=page&orderby=menu_order&order=DESC');
if ( have_posts ) :
while ( have_posts() ) : the_post();
 ?>
    <div class="span4">
        <h2>
            <?php the_title(); ?>
        </h2>
        <?php the_content(); ?>
    </div>
  <? if ($counter % 3 == 0): ?>
 <div id="content" class="row-fluid"></div>
</div>
<div class="row-fluid">
   <?php endif; ?>
    <?php $counter++; ?>
<?php
endwhile;
 endif;
endforeach;
?>
 </div>

<?php get_footer(); ?>