Join at a contact'a address or temporary location as a new temporary location (check in now or future).
Copy temporary location of a contact or otherwise indicate that one is going to be there as well and reshare to one's circles.
This could be a basic I'm going to go to this event as well kind of thing. Deduplicating / unifying when different people create the same event might be a challenge or also not when they then just all show up in the roughly same spot with slightly different names. Might still work.
Join at a contact'a address or temporary location as a new temporary location (check in now or future). Copy temporary location of a contact or otherwise indicate that one is going to be there as well and reshare to one's circles. This could be a basic I'm going to go to this event as well kind of thing. Deduplicating / unifying when different people create the same event might be a challenge or also not when they then just all show up in the roughly same spot with slightly different names. Might still work.