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The correct way to do this is setting the right mimetype. If you see a URI scheme for this type of thing they usually didn't know what they were doing. Support for this goes way back. Add a .ics extension just in case (in url or content-disposition header)

I don't know what I'm doing! Is there a blog or guide about how to do this the right way? Or just a website I can copy off of?

How are you hosting this event? Inside some kind of framework? Just hosting an .ics file somewhere might already do the right thing automatically. If you have a url I can verify it for you