Hi Martin,
Hope so everything's fine at your end.
Typically Ap1200's or LWAPP AP's manage load balancing internally on their own using the Auto-RF features if you are using some 4000 series controllers dunno about others. So this auto-rf features should equally load balance the client across all Ap's, well if that doesn't happen for som e reason then, you may change the configuration to do that.
You may create seperate wlans to be broadcasted through different lwapps with seperate ssid's.
For example,
AP1200-1 broadcasts wlan 1 connecting around 35 clients
AP1200-2 broadcasts wlan 2 connecting another set of 35 or more.. and so on.
AP1200-3 broadcasts wlan 1 again but is at a distance of say more than 100 feet or so connecting another set of 35 or more.. and so on.
Please feel free to contact me if you need any more assistance.
Thanks & Regards,
Karthik Narasimhan