One of our main marketing activities is conference talks. How would I track invitations to such talks and respective attendance in Pipedrive?

I would like to see a list of all people invited to a particular talk (title and time), as well as all people who attended a particular talk. And if we give the same talk (title) multiple times, I'd like to see when the person attended (time). Ideally, I'd like to get conversion rates (attendees / invitations) from Pipedrive as well... is there a way to do this?

I could create an Activity Type "conference talk", but Activities don't seem to be intended for tracking large numbers of independent people, because they are linked to a person or deal. Also they don't have an invited vs. attended concept.

Any suggestions welcome!