Ideas

A gig or a concert

Buy the tickets only when you know who can make it.

The gig has a clock time, but the friends’ meetup does not. Agree in Sopisiko first whether you are going at all, and buy tickets only after the confirmation.

If there are several candidate gigs, add them as alternative times. The organizer locks the one most people can make.

Add the venue address and the doors time to the event. A calendar booking cuts the “where do we meet” messages outside the door.