Grandchild pages summary with pagination

I am having a page named English and it is having some more subpages like Alphabets and Numbers, Alphabets having subpages as A, B, C, D, E, F, G, H, I, J and Numbers is having 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. The requirement is to display all grand child pages in English with pagination, I did manage to display all the grand children pages title, excerpt (Using functions) and first image of the content with read more link but without pagination using the following codes.

<?php
    $pages = get_pages('child_of='.$post->ID.'&sort_column=post_date&sort_order=desc');
    $count = 0;
    foreach($pages as $page)
    {
        $content = $page->post_excerpt;
        if(!$content)
            continue;
        if($count >= count($pages))
            break;
        $count++;
        $content = apply_filters('the_content', $content);
    ?>
    <div class="alternativerow"><h2><a href="<?php echo $page->guid; ?>"><?php echo $page->post_title ?></a></h2>
    <div class="casethumb"><img src="<?php
	  $first_img = '';
	  ob_start();
	  ob_end_clean();
	  $output = preg_match_all('/<img.+src=[\'"]([^\'"]+)[\'"].*>/i', $page->post_content, $matches);
	  $first_img = $matches [1] [0];
	  if(empty($first_img)){ //Defines a default image
		$first_img = "/images/default.jpg";
	  }
	  echo $first_img;
	  ?>" /></div>
<?php echo $content ?><a href="<?php echo $page->guid; ?>">Details</a> </div>

Can someone please help me in putting pagination to this?