One way to customize plugins is to extend it. Creating a child plugin is not practical because this only works in themes. Themes have a very specific set of behaviors and plugins are completely different. The right way to customize a plugin is to get in touch with the plugin author and let them know of the changes you’d like to see. However, if this doesn’t work, the best way is to extend it. However, take note not to modify its core. The easiest way to do it is to create a functionality plugin that will run alongside it. You can also use plugin dependencies to control when the functionality is activated.
To learn more on how to do it, read this post: http://wptavern.com/how-to-extend-a-wordpress-plugin-without-losing-your-changes