Fly Deterrent? I am having a group for my 2 year old son and...

I am having a group for my 2 year old son and the flies where on earth I live are terrible. I will serve food within a sunroom, but it will mainly be an outdoor knees-up. As it will be about or above 30c I am looking for something that I can use to deter flies. I hold Aeroguard but is there anything I can use contained by trees, the shed roof, or on the ground etc that may deter the flies from even being within the area. Any suggestions would be appreciated.
Don't ponder this is bad the wall, but...
Answers:    Your choices are controlled.
Either you get a pest control company to spray the nouns just until that time the party ( space spray not surface spray).
Or you buy some fly bait. There are a few arpound but one made by Bayer Bayrepel is excellent but I am not sure if you hold it where you are. Others are Golden Malarin. See what your local Hardware store have. Then put fly bait in trays (Out of realize of kids!) for a few days before the entertainment, flies feast on it and die,