I'm no lawyer, I'll state that up front (but I did stay at a Holiday Express once). My take on this is that the FAA commercial fine is probably the least of your worries. After all 5k's are full of lots of people, the exact thing you are strictly forbidden to fly above and around by FAA. Not to say that it can't be done safely from a distance, but be careful. There are personal injury lawyers out there that specialize in drone injuries and trained to fetch top dollar.
A plaintiff just needs to prove that you've acted negligently by failing to act with "reasonable care" (aka: flying over a crowd) and proving that your negligence actually caused the accident, and lastly that the injuries were caused as a result. They can recover for both economic and non-economic losses, including medical bills, pain and suffering, lost work time, legal expenses, incidental expenses and punitive damages. You can also be liable for criminal negligence if the incident is serious enough. We're talking jail time and massive amounts of money.
Drones and people don't mix.