Looking for a plugin …

Hello guys.

I need your help on finding a plugin.
This is how my WP site structure looks like:
– gyms (custom post type) with few custom custom fields for hours and sports.
– coaches (custom post type) with custom fields for coach thumb and some other infos.

Now, how could i add a custom field that has a checkbox list with all the coaches on gym post? End at the end display the checked coaches thumb on page?
Is there a plugin that can work the connections ? (i didn’t find one using search)

Right now i’m using: Custom Post Type UI and Advanced Custom Fields plugins.

Thank you.