Enable on the physicals usually. I have netflow running at home on my 1841, and have netflow on my WAN port, and one subinterface ( I don't want information from the other sub-interfaces).

Netflow would give you information on a connection level. Your config looks fine, have at it. From my experience 90% of SNMP is configuring your reporting tool.

Included in the download is the NetFlow Configurator Tool, which helps network managers configure NetFlow Version 5 via SNMP on supported Cisco devices.

A deployment methodology for profiling difficult endpoints designed to enable NetFlow when needed, and disable when not.