I have been to numerous competitions as a cook, judge, and even trained and ran the judging at a backyard KCBS style event several years ago for a four meat, overnight comp. I have also organized and run one day 3 meat "backyard" events. At none of those events did we need a licensed kitchen and teams purchased and brought their own meats. I have never judged or competed at any event where the meat was provided. Teams purchased their own meats and had those meats inspected on site before the cooking began. Inspection included checking the temps of the meats (with one of those temp guns) and making sure meat was packaged and not pre-seasoned or pre-marinated.
If you intend to sell bbq to the general public, then yes, you need the licensed kitchen and health permits and have everything being sold to come out of that kitchen and be to code. We ran a bbq concession for a charity at the BBQ Comp at the Aurtry Museum in, I think, 2006 and made $4000 after expenses, so it can be a good way to raise money since the smells from the teams make folks hungry. The competitors need to be told their meats can't be sold to the GP.
It sounds like you are doing a one day event. So you need to limit the meats cooked to things that can be done in a few hours. Our 3 meat contest were chicken, pork ribs and tri-tip because all had fairly narrow cook windows. Maybe since you have a lot of pork in the area, you replace tri-tip with sausage.
There are A LOT of details, A LOT of planning, and the judging has to be run by someone who knows what they are doing. You need a judging system in place which can be clearly explained to both cooks and judges. KCBS style judging is not practical unless you have access to the KCBS weighted computer scoring program. So you have to come up with your own -- judging categories (appearance, taste, tenderness, not all of these, something else?), scoring, and descriptions.
Where will this be held? Will there be a charge? Can charcoal be used in the area? How will you dispose of live coals afterwards? Do you have access to water and restrooms at the site? Electricity? How is grey water to be handled? What are the fees for using the site and providing amenities and will these be passed on to competitors? Will you have an "Anything Butt" and/or dessert category?
Are you giving prizes, trophies, ribbons -- out how far -- top 3, top 5? Are you having a Grand Champ and Reserve Grand Champ or just winners in the categories? Are prizes going to be donated or come from sponsors or come out of the competitors fees? At our true backyard event, I baked all the prizes but we had no fees to enter because it was held as part of a block party. Also you need a timeline established for when cooks show up to set up, when the cooks meeting is held, when the judges meeting is held, when your turn ins are and when awards are announced.
If I have not depressed or discouraged you, please feel free to PM me and I will share as much info as possible. Setting them up is a ton of work, but it can be a fun day when all is said and done.