Redirect all child posts to parent with query string

Hi, looking for some help with this.

We have a “parent” post where a user can click a button that runs some script in the back end that generates a post. Right now that generated post is a totally empty custom post type that is a child to that parent post. We want all of those user generated posts to show up on our website as if they were full posts. Then when the user clicks on a child post, they are directed to its parent, and a parameter is passed from the child to the parent.

Basically we want all child posts to redirect to the parent, with a query string parameter that is unique to each child. The template of the parent post will interpret and display data based on the value of the parameter.

We tried setting the permalink slug of the child to the same slug as the parent, and added the query string but that just ended up redirecting the parent to the child post.

Ideas and suggestions would be very helpful. I’m happy to try to explain the circumstance in more detail if need be.

Thanks so much!