[Kevin]

Your best bet is to assume people are going to do everything to break the rules and to structure things so that they are exposed to the least amount of risk possible. You'll need buses to and from the event, hire a cash bar with its own liability insurance. You'll need to have adequate security using wristbands for people who are of age. Ideally, you'll hold this event at a hotel or bus over to a hotel after the event where everyone can safely sleep it off.

I hate the idea of having officers check IDs, use your security people so that there is no resulting drama from any shenanigans which may ensue.

As far as discipline, it's not any of our places to even suggest what your organization's internal standards should be. It's hard to imagine that your chapter has never had to deal with a drunk or disorderly member in its entire history. Use that experience, don't reinvent the wheel.

Also, there should be some members--officers/alumnae advisors who should be on the site who remain sober and able to make major decisions should anything bad happen.