Set up a code of conduct
Think carefully about the Terms and Conditions of participation. You don't need to be a lawyer (though having one accessible to you can certainly help clarify tricky questions). What are the kind of areas of potential conflict? Do you need special terms to use the facilities, to access datasets or other resources? What expectations should participants have of the organizers, the team? In particular when it comes to maintaining a healthy social setting, having a Code of Conduct with a strong policy against discrimination and various forms of abuse is important.
Or maybe it's enough for us to Be Excellent To Each Other?
A generic and configurable Code of Conduct for hackathons