Steve

your solution may require a network utilizing Cisco mesh AP'S depending on the location of available wired network cnnections. to answer the rest of your question a site survey needs to be done to determine the location of the AP's and the type of antennas required, sources of interferance, etc.

covering this large of an area can be a challenge and depends on the existing infrastructure and the physical layout of the yard buildings, height of stored items. are there light poles, is 24/7 power available at the poles.

Good luck with your project

Bill