Networking :: Isolating Part Of Network

I am trying to set up a free wireless network for clients for a small business. I have a wireless router that I plan on hooking up to our main router. I want to keep all the computers that are associated with the wireless router from being able to access the rest of the network hooked up to our main router. I think one solution might be to put the wireless router in a DMZ. I think this should isolate it from the rest of the network (and have a side-effect of sending outside traffic to the wireless router, which shouldn't matter). Will this work? Also, if I just make both routers have the same subnet (e.g. 192.168.1.x), will my wireless router just filter out requests for computers on our main network as requests for (non-existent) computers on its local network? Any other ideas are welcome.