I can get you details of specific charities which funding only goes to supporting what the cause stands for, you can also fund direct projects within a charity in some cases which I can also provide details of.....
Main issues would be things like event insurance etc depending what you decided to do. We use land for Pete's model club and we have to provide things like insurance proof, H&S information, risk assessments, details of first aiders on day etc etc which is a pest
Where were you thinking of hosting it and when?