Just a guess, not tested, but a thought: can you give this parent role you made the 'view without participation' permission in just that course? Then they don't need to be enrolled and then should also not appear in the participants list. To get the email event reminders (is that a forum?) they should still be able to subscribe to the forum... You can test it out with a different role and see if that suites your need.
Roles and permissions
Parent Role and hiding from Participants
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