Function to delete a post, it’s children and it’s grand children (half way there already)

Here’s what you can do:

1. get all the ids of direct children
2. get all ids of grand children
3. combine

4. trash

   function trash_redirection_frontend($post_id )
   {
   if ( filter_input( INPUT_GET, 'frontend', FILTER_VALIDATE_BOOLEAN ) ) {
   
       $args = array(
           'posts_per_page' => -1,
           'post_parent' => $post_id,
           'post_type' => 'bucket',
           'fields' => 'ids', // get only the ids, it's all we need
       );
   
       // get all children ids
       $children = get_posts( $args );
       $all_parents = array_merge( [ $post_id ], $children );
   
       // get all grand_children
       $args['post_parent__in'] = $children;
       unset( $args['post_parent'] ); // we're using the above array now
   
       $grand_children = get_posts( $args );
   
       // $all_posts now contains all affected ids
       $all_posts = array_merge( $all_parents, $grand_children );
   
       foreach($all_posts as $child){
           wp_trash_post( $child ); // use this unless you have good reason to query directly
       }
   
       $referer = $_SERVER['HTTP_REFERER'];
       wp_redirect( $referer );
       exit;
   }
   }