A cheaper option would be putting up a couple Ubiquiti UniFi APs which come with a 'free' software based controller that runs on Windows or Linux.
How big of an area is it? How much WAN bandwidth do you have to work with? Have you done a wireless site survey to get a rough estimate of the amount of APs you may need for coverage? Do you have someone familiar enough with the equipment to set up a segregated guest network? Do you have existing network equipment like PoE switches or would you need to locally power each AP at its location?
Kind of a lot of factors to consider if you want a 'proper' type of deployment instead of buying some random consumer grade router and blindly hoping for the best. You might be able to pick up one or two UAP-PRO or UAP-AC access points and run the software controller as a cheap pilot to see if it can do what you want.