Charity event

Hi I am organising a charity event for 5 students who have been chosen to go to Namibia to help build a school, part of this is to help the students rebuild their own confidence after various forms of being bullied. I have never done anything like this before and am quite terrified to be honest, but I am looking for comedians to put on a show for the night of the 28th November, now I don't expect anyone to do it for free I understand that you of course have costs and lives to live but at the minute I am being quoted £300-£400 which we just can't afford, we will also have PA system as we have an AC/DC tribute band to play last off so if anyone could attend or even offer me some advice it would be much appreciated. Thank you