They may feel like they won't know anyone. While this may be true, they should definitely know some people after the event and make some nice contacts. Seemingly silly but helpful ice breakers help get a crowd talking. Judges can reminisce about eating outside on the covered patio in a hail storm or being able to trace the fastest path from the University Inn to the College on a map. Regardless of the size of the crowd or whether you decide to use ice breakers or not, a social hour prior to the more formal part of the activities should be planned.
Food is a wonderful excuse for socializing.
However, be aware that because of the many demands on everyone's time these days, an event should not be an inconvenience to attend. Weekend activities that include the participation of an alumnus' family work very well. The Nevada alumni chapter held a tailgate barbecue before a University of Nevada football game. Besides holding food or drink gatherings, there are many other ways to gather people together. Perhaps there are opportunities in your region like clam bakes, sporting events, hometown festivals, or harvest parties that would serve as a fun way to gather alumni.