Displaying your child pages on a parent page in a responsive grid is easy with smartshortcodes.
Firstly go to plugins and turn on smartassess [shortcodes]
Now go to the back end of your page, in the right hand side bar half way down the page you should see 'Page Attributes.'
In the 'Parent Page' section, set the parent page that you want the pages to display on as a grid.
Simply add this code to the parent page: