Hey Tac and welcome back to the forums. 🙂
I’d be happy to help but first off, I do want to note that we are fairly limited in how much we can support custom development questions like this. At the very least, I’d be happy to at least point you in the right direction, if I can.
The Community Events submission form pulls the event admin editor directly and applies it to the front end. As such, whatever is used in the back end will also be used on the front, so you would need to change the admin view if you want the change to be reflected on the front end.
Unfortunately, editing admin views is much more complex than the front-end calendar views themselves — in fact, editing those files is something we do not recommend because those changes would likely get lost in a future plugin update. Our documentation is available for your reference, should you want to make changes to the admin interface.
My recommendation is that, if it’s a styling issue, to try customizing the checkbox styles with CSS.
If you’re more concerned about the functionality of using a checkbox rather than another control (e.g. radio button), then I think it would be wise to enlist the help of a freelancer to responsibly make that customization.
Sorry I don’t have a concrete answer for you, but does this at least help get you started? Please let me know.
Thanks,
Geoff