Hey Janine,
I have a client with the same need and we finally settled on "Stout Google Calendar" plugin.
You can see it in action here
http://smarterdirectsalestraining.com/calendar
She is still working on her site so you'll need to go to Nov or Oct to see how it looks with an entry. She is able to copy/paste the link to her registration page right in google calendar and it automatically updates the site calendar.
I don't like how it cuts off the title but haven't found an easy way to fix it. You can set it to default to "agenda" view then you won't have to worry about that.
`C