Pay for some private military contractors, doctors, and a standby helicopter. Split the cost.
EDIT: If PMC are too militant, just any lenient security company would do. I don't really see how this is a problem. Think of it as a big festival with less alcohol and run for a longer time period.
IMO private military contractors are pretty much a non-answer to the problem of policing. I'd go as far as to say that PMCs are an inappropriate solution to any problem that doesn't involve lots of people getting shot.
Festivals have to deal with minor security, not criminal problems. Police are still around - whether patrolling the area, or in an on-site office, or on the end of a phone call - to deal with any major problems (all the way up to rape and murder).