Ok, you will need to get Internet in the business from a provider, then you need to setup your wireless network. To many wireless routers and you will over crowd the space you are going to have to find the right spots to out the wireless routers, once you do mount them to the Walls, my guess would be 2 to 3 maxs but then I don't know the size of room. The below may help, you may need to bridge the wireless routers also
http://windows.microsoft.com/en-GB/windows-vista/Setting-up-a-wireless-network
http://www.cisco.com/en/US/products/hw/routers/
Best to call cisco or some other store tell them what you plan to do and they should give you the right router for the job hope it helps.