Create page excerpts for landinpage

You can get an array of child pages using get_children. Use the parent page’s ID as post_parent.

Once you have the array, you can loop through them and display whatever info you want. For example, to show the page title (linked) and the excerpt you could do:

$args = array(
    'post_parent' => $post -> ID
);
$children = get_children( $args );

if( $children ):
    foreach( $children as $child ):
        $permalink = get_permalink( $child -> ID );
        echo '<a href="' . $permalink . '">' . $child -> post_title . '</a>';
        echo $child -> post_excerpt
    endforeach;
endif;

You mentioned using the read more link – that’s actually added to the post content, not the excerpt.

How to use ‘Read More’ – create a loop

Get the children as above but create a loop from the results. Using the_content() will show the truncated content where you have added a ‘Read More’ marker. Do this instead of the if statement above.

foreach ( $children as $child ) : setup_postdata( $child );
  the_content();
endforeach; 
wp_reset_postdata();

You can see more examples on the get_posts page