posts by parent page in sidebar

I am trying to hack the sidebar — or even replace it with an included file — so that I have the latest 5 posts from a particular category based upon the parent of the actual page being displayed.

<?php
if (125 == $post->post_parent) {
$args = array(
    'numberposts'     => 5,
    'offset'          => 0,
    'category'        => 5,
    'orderby'         => 'post_date',
    'order'           => 'DESC',
    'post_type'       => 'post',
    'post_status'     => 'publish' );
}

get_posts( $args );

?>

Can someone offer advice?