Attempting to get number of grandchildren of page in WP_Query loop

Found a solution!

$inner_query = new WP_Query(array( 'post_parent' => $parentid, 'post_type' => 'location', 'posts_per_page' => -1 ) ); 

    $countchildren = $inner_query->post_count; 
    $counterz = 0;
    if ( $inner_query->have_posts() ) {
       while ( $inner_query->have_posts() ) {
          $inner_query->the_post();

           $posterid = get_the_ID(); 
           $inner_inner_query = new WP_Query(array( 'post_parent' => $posterid, 'post_type' => 'location', 'posts_per_page' => -1 ) ); 

           $counterz = $counterz += $inner_inner_query->post_count; 

        };
    };