At the start of your next year's event, you will probably want to invite your participants from last year's event to sign up again for this year's event.
As well, you may want to send a separate email to your team captains from the previous year to encourage them to setup their teams again and recruit team members.
Follow directions to prepare an email by referring to the instructions at either link below:
Wizathon: Sending a Mass Mailing to Your Participants
Wizathon: Sending a Mass Mailing to Your Team Captains
When you get to the step to Send your email, choose All Participants/Team Captains from the Last Event.