Hi there Edward, thanks for getting in touch!
Great question. I think the best route for setting permissions for posting event posts is to assign each of your users into two different categories. For example, you could divide them between the Author and Editor roles.
Then you can use this snippet in your functions.php file to remove event posting and editing capabilities for one of those two roles. The snippet contains all of the existing default WordPress roles and all of the plugin permissions, so you can tailor it to suit your needs.
Does that make sense? Will that work for you? Please let me know. 🙂
Cheers!
Geoff