Edits to Excerpts from children Widget – Thumbnail image not working

I’ve been working on editing this widget a bit so that it will work with calling the built in excerpt editor of WP. I managed to get that part working, but now the thumbnail is no longer working. I’m hoping someone can have a look at the code and see if there is something I’m missing. I’m no PHP expert, and have spent hours going through the forum trying a lot of ideas to no avail.

Another idea I have is to create a template file for a page with subpages, but I’m hitting a brick wall here too.

function excerpts_from_children($attrs) {
    global $wp_query;
    $params	= $wp_query->get_queried_object();
    $children = get_pages('sort_column=menu_order&parent=' . $params->ID . '&child_of=' . $params->ID);

    $output = "";
    foreach ($children as $child) {

        $output .= "<div class=\"excerpts-from-children\">";
        if( has_post_thumbnail() ) {
          $output .= "<img src=\"" . $child->the_post_thumbnail( 'thumbnail' ) . "\" title=\"" . $child->post_title . " thumb\" />";
        }
        $output .= "<h3>" . $child->post_title . "</h3>";
        $output .= "<p>" . $child->post_excerpt . "</p>";
        $output .= '<p class="read-more"><a href="' . get_bloginfo('url') . '/'. make_clickable(get_page_uri($child->ID)) . '">Read more &raquo;</a></p>';
        $output .= "</div>";
    }

    return $output;
}