At a private party/at home, you can give a child between 5-17 alcohol with parent/ guardian permission. You cannot sell it to them though. You could attempt to contact parents to gain permission to give them alcohol of you know who is under 18, but they may just fake permission. You could include it on the invite that they either need written permission from parent or id, but it relies on the parent having knowledge of the party/ alcohol issue. At least if you are providing alcohol they may be less likely to smuggle it in (maybe). Also many halls around here won't rent out for teenagers parties.