Once you "what if" common issues like weather, traffic flow, and normal criminal activity, you can graduate to the "what the hell" questions. You know, like when you hear an explosion, turn, and say, "What the hell?"
So, what is your contingency plan for a hostage-taking emotionally disturbed person, an active shooter, a riot, or a terrorist attack? If you're thinking planning for a terrorist attack is a bit over the top, let me reframe the issue for you. Aside from the potential death, mayhem, and destruction a suicide bomber might cause, if you didn't consider it, when it is all said and done, who do you think they are going to blame for the mess?
After the agency gets reamed in the media, they always get rid of the lowest common denominator...you. The unspoken collateral damage in any bureaucracy is always the scapegoat. Therefore, anything that involves large gatherings is suspect and deserves the best planning possible. There are limits to any organization and it may come down to just having a few extra officers on site, identifying a landing zone nearby for MEDEVAC, establishing a possible staging area in case of an emergency, and briefing any surrounding agencies in case you call for assistance. It may be very minimalistic, but it still qualifies as contingency planning in anybody's book.
Horses, Dancers, and The Three Kings
For the last seven years, my jurisdiction's Hispanic community has celebrated a holiday related to Christmas often called "The Three Kings." The local Hispanic Business Council sponsors this event, which typically draws between 5,000 and 8,000 attendees. It's an event that offers free food, music, toys for children 12 and under, and a raffle of between 25 and 100 free bicycles.