Adding members to activity log

I created an event for a hike coming up this Saturday so our Cubmaster could add participants after the hike. I just wanted it on the calendar. When I go to Edit, the only thing I can edit is address, name, etc. There is no longer an entry for participants or the mileage. Is there a way to edit this?

Did you make an Event in Calendar or an Activity - they are different

It was an event…but to be honest, I don’t understand the nuance between the two very well.
It now appears to let me add people. Maybe it just locks until after day of the event…which is fine. Maybe just my lack of understanding. But i wanted to create something so any parents or older scouts could add if I miss them. I think it seems OK now.