I have been to other cycling events where they have had a secure area where you can easily leave bikes. They often use a ticket or wrist band system matches tickets given to you, to corresponding tickets attached to bikes. This way no one, apart from the security staff are allowed into the secure area.
Yes, this would mean more work for the organisers and they would probably become liable if bikes were lost or damaged. On the other hand it would make for a more enjoyable and relaxing time for exhibitors.
9/16" Suntour BMX MP-1000 pedals / 56 tooth TA 6-bolt chainring.(I'm not bothered if the teeth are worn or damaged)