Hi there. I'm just going through the code in your plugin to try to figure out if it's going to work for my client's purposes, and wow, you really outdid yourself back there ;-)
I'm sure as I get deeper into it I'll have some questions, but, just wanted to get this to you real quick for now ...
On lines 108-109 of event_regis.php you've got this "Event_Registraiton_Calendar" little typo.
And thanks so much for putting this code together. I've been working with different event calendar/management etc., code in wordpress for some years now and pretty much everything always falls short in one way or another ... not surprisingly, as there are so many different ways that people need to use such things ... I'm curious if you've considered using custom post types for the actual events in this though ... with custom taxonomies for the event_type and custom fields for all else? Is there a specific reason that you felt it would be better to just sidestep all the wp stuff in general?