The classic pair I’d use is netstumbler and wireshark. But with 50 access points,
you’re going to have a lot of data to collect and analyze. Maybe MRTG (Multi-Router Traffic Grapher)
would be the thing. If your APs will respond to SNMP or RMON queries, MRTG will make a lot of pretty graphs
that’ll tell you the load on each device.
Google will tell you where to download all of these. They’re free.