Content type which contains a content creation as a slip form I'm quite new to Drupal and I've encountered a quite complicated problem.

I've created a role called "Event coordinator" authorized to create a content type entitle "Events" that has a title and and a description, and for which comments are disabled. Here is a sample of it:


Title: "Join Our Club".
Description: "It will be fun".


I've also created another role called "Audience" which will be used by the user who will attempt to join the event detailed in the content created by the "Event coordinator". 

The "Audience" should create a "Slip" content which will have a request message. And it should be sent to the targetted "Events".

A "Slip" that gets created will be put (somehow) in another content which is the "Events". The "Event coordinator" then will choose whom will join an event based on the "Slips" that were created.

Only the "Event coordinator" and the owner of a slip (created by "audience") will be able to see a "Slip".

I've tried to use the "entity-registration" but it's not that flexible. I mean as an "Event coordinator" I'm not able to see all the "Slips" from all "Events" I created. It will just show the "Slips" when you view the content of a single "Event".

Any suggestions about which module(s) I could use to implement this?
You may use Organic groups module


  Enable users to create and manage their own 'groups'. Each group can have subscribers, and maintains a group home page where subscribers communicate amongst themselves.


"event-coordinator" will be group administrator and he will create and edit any content in the group. "audience" will be usual group member and he will edit only own content in the group