Although I'm not in your neck of the woods, I am an insurance agent in Illinois and specialize in Special Event Insurance Policies (among other things...). You can purchase a short term special event policy for 2 days that the event takes place. In Illinois you can expect to pay around $250 or so for this coverage. Although you being sued is not likely, this policy at the very least affords you legal representation/defense in the event a frivolous suit is brought against you. OR in the event you do screw up and get somebody sick, this policy will respond as well. I would not be concerned with judged food, whether the contest organizers like it or not, they cannot avoid their liability in this situation. In bad claims, where many people get sick or someone get seriously hurt, I don't really think a signed waiver is going to matter much. EVERYONE involved will be brought into a lawsuit and usually the deepest pockets (or the one(s) with the highest policy limits) and the one's with the worst defenst lawyers get hit the hardest. It is smart to cover yourself here. A personal umbrella is also an option, BUT the umbrella policy will only respond when any underlying policy limits are exhausted. So, basically, if your homeowners policy does not cover a loss, your personal umbrella most likely will not respond in this situation. Keep in mind an umbrella policy only applies once underlying limits on another policy are exhausted. For example, if you have $100,000 liability limit on your auto policy and a judgement of $500,000 is awarded in an accident where you severely hurt someone, your umbrella policy would pay the amount awarded OVER the $100,000 limit of your auto policy. $400,000 in this case or up to the umbrella policy's limit. SO, the safest way to cover yourself is purchase a special event policy, but now you've just increased your comp costs a bunch. Your current homeowners policy may or may not provide coverage in the event that something happened at a comp. I'd get a written statement from your agent indicating that coverage would be provided in this situation. ALSo, keep in mind, you must be proven NEGLIGENT to be deemed liable.
All that being said, I don't buy event policies for the comps I do and don't plan on it in the future.
sorry for the ramble, but in our business there is never an easy, short answer.
md