My function echos only "array"

I'm trying to create visual composer extension that displays all the child pages.

Somehow it only displays "Array".

Any ideas?

function childpages_func( $childpages = '' ){
      $childpages = get_pages('child_of='.$post->ID.'&sort_column=post_date&sort_order=desc&parent='.$post->ID);
        foreach($childpages as $child){
            "<div>
                <a href='.get_page_link($child->ID).' title='.$child->post_title.'>
                    <img src='.wp_get_attachment_url(get_post_thumbnail_id($child->ID)).' title='.$child->post_title.'>
                </a>
            </div>";
        }
        return $childpages;
    }

    /* Display Child Pages */
    function vc_doo_clip_child_pages_func( $atts ) {
     extract( shortcode_atts( array(
            'cp_header' => 'cp_header'
        ), $atts ) );
         $end_content = '<h2>'.$cp_header.'</h2>'.childpages_func().'';

            return $end_content;
    }

Any help will be greatly appreciated ;) Thanks!