Spark arresters and other safety equipment are nice. It is a good idea to always start with a good location, and safe practices. These other things just help out. I don't rely on them for fire prevention.
If your choice is to build close to the chicken house or barn, then consider a stray spark. I would rather replace a chicken coop than the entire barn. also the hay can ignite fast, starting other things burning.
If it was my call, I would build at least 3x the height of the chimney away from anything you can't afford to lose. So if you have a flue top of 15 feet above ground, a 45 ft burn free radius, should be fine.
Having said that the odds are low of starting a fire from your flue using charcoal, coal or coke are even less, but this is a long term shop so why have to move it later? Why risk your property by making a hasty placement decision.