i used to throw event like this man i hate to say it but liability is a bitch, like im all for under 18's partys but even on private property you have to have some sort of public liability insurance. Im not saying you HAVE to but if shit goes wrong or the cops show up then youll have issues, you also have to consider the licencing of music to play live music somthing that might help you ALOT is getting the local PCYC involved they will provide staff and local government backing which would make your life easier