If you want to be sure to all get into the same event, check the box "Only get selected tickets if ALL selected are available."
The first friend whose wishlist processes will get the tickets for everybody. That will block off the time from your schedules, so you cannot get another ticket to an event at the same time. This should prevent you from ending up with two tickets to the same event.
If you do somehow end up with duplicates, drop them from your cart before checking out.
All the tickets successfully obtained from your wishlist go into your cart; you pay for them.
Something to be aware of when buying for friends:
If you choose shipping, all the tickets will go to the purchaser, but Will Call separates the tickets by whose name is on them, so each friend will have to pick up their own ticket.