This plugin is very simple and straightforward. Just enter ?{list}? on each parent page or post where you want the children listed. Put it anywhere in your content and that is where it will show.
Then in your css..
.subpage-style { Put your styles here };
Easy as pie!

Andy's List Subpages Plugin

Nice and simple plugin that lists the children of a certain page or post in…

bobbingwide

Use the Children block ( oik-sb/children ) to list children of the current content as links. 
Works for any hierarchical post type which supports page-attributes, such as page.

SB Children block

List children of the current content as links.

Andy's List Subpages Plugin vs SB Children block