Wireless Router Logging Software?

Hello TR.
I am implementing a cyber cafe type deal in the local Mall. People can walk in and connect to the internet for free… that is done.
I want to be able to log the connection dates and times and view my statistics for connections. Trying to create a benefits vs cost model at this location to see if it is beneficial to move this to other locations.
Details:
Just a connection to a WRT300N LinkSys. SSID is changed, password is changed. And it is not connected to my network.

Any suggestions for logging? Third party tools? Or do you suggest I secure it, put it on a small network and monitor the traffic?

Thanks!