Small business router that shows bandwidth usage graphs in the admin panel

I support a large number of public libraries that are having their networks upgraded in response to a grant application. These libraries are generally home to between 6-15 computers and have little or no tech services either onsite or contracted remotely.

In order to justify current and future purchases, a number of the libraries have requested routers that can provide bandwidth usage graphs that they can show to their managing boards. Is there a small business router that displays traffic graphs in the router administration web interface?

The router needs to suppport DHCP and basic firewalling. No other features are required. Further, the reports just need to show overall trends. It is not necessary to show traffic by IP, by protocol/application, or by time of day. They just need an overall week to week, month to month, trend line.

I'm familiar with MRTG/PRTG/tools that collect SNMP data from the router, but the libraries don't have the expertise for the configuration. I've considered installing the tomato firmware on some cheap home/home office routers, but if there's a commercial product that can be purchased that would be significantly simpler. Also the library boards would be much more likely to approve the purchase of a commercial product over a 'hacked' one.

Any assistance would be appreciated.