Sending an event invitation reminder is a great way to boost registrations for your event. Like all messages sent from Marketing Cloud, make sure it's as targeted as possible. In other words, if someone has already RSVP'd to your event, a reminder invite isn't relevant to them. Worse yet, it confuses folks, making them think their attempt to register failed.
Even those without a Cvent login can access data through a password-protected URL whenever they fancy, and, best of all, without needing to pester you. You'll just need an eComm specialist to get a Report User added to Cvent and create the desired Parked Report.