AETHERPHON, global theremin family

I have my first solo gig coming up soon. On December 3rd, I have a half
hour of time to provide music for one of the large radio clubs in this
area. The event is their yearly Christmas banquet. I am to provide
"atmosphere" prior to the start of the meeting. After dinner, a quartet
of kids of one of the members will sing. Probable attendance is around
50. I figure I should plan for one piece every 5 minutes. Is this too
ambitious? How many pieces does the assembled multitude think I should
plan for in a 30 minute period? I realize there will probably be LOTS of
interruptions as people wander in to the meeting and say "GEE WHIZ",
stumble into my playing field, etc. 

I know a lot of these people, so this is kinda a friendly crowd, with 
no rotten veggies anticipated. Any ideas on dress? Everyone will 
probably be in their street or after work clothes, so its not a formal 
atmosphere in the least.

Philip