Linking CiviCase with a CiviEvent
Who are you organising the event for? Your organisation seems to be the most natural, but having a client of a case (used to be?) is tricky. If it doesn't work easily with your org, I'd put the event manager as the "client".

As for creating the link, I'd put a custom field (integer) that contains the id of the related entity. I'm not sure I'd put the event id on the case of the case id on the event, depends of your workflow and which one is created first, and a tiny extension to display the id as a link instead of the number.

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