Show node only to node author and author that is referenced by node
You could use Node Access User Reference for this task:

Gives content access permissions to users for content that references the users with User reference or Entity reference.
This is great if you want your content authors to be able to choose additional authors, or choose who can view their content, as well as being able to display the list of authors or viewers within your content, or in views displays.

Or you could use OG groups for something like this as well: https://www.drupal.org/project/og It may be a little harder to setup at first but certainly more a more flexible option.