get_the_excerpt()
won’t work in your code if you add content to the main WYSIWYG editor instead of the excerpt field.
Check how get_the_excerpt() work and try to find out filter hook with get_the_excerpt
hook name.
Please try the following code, hope you’ll get the expected result.
<div class="parent page">
<?php
global $post;
$args = array(
'parent' => $post->ID,
'post_type' => 'page',
'post_status' => 'publish'
);
$children = get_pages( $args );
if ( ! empty( $children ) ) :
?>
<div class="childcells">
<?php
foreach ( $children as $post ) : setup_postdata( $post );
?>
<div class="childcell">
<?php if ( has_post_thumbnail() ) : ?>
<div class="thumbnail"><?php the_post_thumbnail( 'small-thumb' ); ?></div>
<?php endif; ?>
<div class="myclasstitle"><?php the_title(); ?></div>
<span class="desc"><?php echo get_post_meta( get_the_ID(), 'desc', true ); ?></span>
<div class="excerpt"><?php the_excerpt(); ?></div>
<a href="https://wordpress.stackexchange.com/questions/301420/<?php the_permalink(); ?>" rel="bookmark" title="<?php the_title_attribute(); ?>">Read more</a>
</div>
<?php
endforeach;
wp_reset_postdata();
?>
</div>
<?php endif; ?>
</div>