There will be umteen regulations regarding tempory power supplies, so ensure that ONLY profesional electricians are involved in the installation testing and certificating of these supplies, this is NOT A JOB FOR ANY WELL MEANING HANDY MAN. RCD protection and earth electrodes will be required and appliance testing of all equipment concidered. Contact your electricin in plenty of time, at least a week in advance. As for a 100M to 200M cable run? A fairly hefty and expensive cable will be required, 10mm,16mm maybe 25mm, and conderation about any roads and access points so as cars, vans or even pedestrians won't cause any dammage or be injured themselves. I asume you have insurance cover for the event? They will wash their hands over any claims if if the instalation is not 100% pukka. I have worked in the electrical industiy for more than 40 years this and is not a two hour job more like two days maybe three and it will have to be cleared up after the festival.