I'll second Adam's general comment... That equipment is not designed for the purpose that you are trying to use it for...
Almost any commercial grade WiFi solution would have guest access with splash-pages built in allowing you to run both internal corporate WiFi and guest WiFi securely on the same access points.
And 2 firewall/routers re-purposed as WiFi access points covering 53 rooms?!
Sorry to say but this just doesn't sound like a viable solution.