Shortcode with exclude post ids

<?php
function displayChildPage($atts){
   extract(shortcode_atts(array(
      'parent' => '',
      'icon' => false,
      'exclude' => ''
   ), $atts));

    wp_reset_postdata();

    global $post;

    if (empty($parent))
        $parent = $post->ID;

    $output = "";

    $args = array(
    'orderby'       => 'menu_order',
    'order'         => 'ASC',
    'post_parent__in' => explode( ",", $parent),
    'post_type'     => 'page',
    'post_status'   => 'publish',
    'numberposts'   => 24,
    'post__not_in'  => explode(",",$exclude)
    );
    $query = new WP_Query( $args );

    if ( $query->have_posts() ) :
        $i = 0;

        while ( $query->have_posts() ) {
            $query->the_post();
        if($i % 4 == 0) {
            if($i > 0) {
                $output .= '</div>';
            }
            $output .= '<div class="row no-margin gutters split-extra-small">';
        }
        $output .= '<article id="post-' . get_the_ID() . '" class="' . implode(' ', get_post_class('column-6 grid match glow text-center',  get_the_ID())) . '">';

            $thumb_id = get_post_thumbnail_id();
            $thumb_url = wp_get_attachment_image_src($thumb_id,'medium', true);

            if ($thumb_id) {
                $output .= '<a href="' . get_permalink() . '"><img src="'. $thumb_url[0] . '" alt="' . get_the_title(get_the_ID())  . '" /></a>';
            } else {
                $output .= '<a href="' . get_permalink() . '"><span class="fa-stack fa-3x"><i class="fa fa-circle fa-stack-2x"></i><i class="icon icon-' . $post->post_name . '  fa-stack-1x"></i></span></a>';
            }
            $output .= '<h3 class="entry-title"><a href="' . get_permalink() . '" rel="bookmark">' . get_the_title(get_the_ID()) . '</a></h3>';

        $output .= '</article><!-- #post-## -->';


        $i++;
        }
        $output .= '</div>';
        $output .= '<!-- subPage -->';

    endif;
//
    wp_reset_postdata();

    return $output;
}
add_shortcode('childPage', 'displayChildPage');