Just to be clear: You want to give wireless access to 200 clients over two APs *?at the same time?*
That would be a Very Bad Thing, and almost certainly not possible.
Generally speaking, with "normal" traffic (no such animal exists), you can expect to run 20 - 30 clients tops per AP.
It is not likely that you can impose your restrictions at the AP level. More likely, you'd want to do it at the switch, possibly at the router.
The problem is that the AP acts as a hub: shared bandwidth, and collision avoidence. Basically it boils down to every client getting a timeslot to communicate. When you have too many clients on a single AP, the clients are not talked to often enough, and you get association drops. Before association drops, you get really poor performance that progresses to request timeouts.
The other issue is the uncontrolled mix of clients that you're likely to see. If one client is using 802.11b (11 meg), the net effect is an additional drop in available bandwidth.
The bottom line is that it's not a plan that's likely to succeed.
You may want to investigate 802.11a (5GHz). It has more non-overlapping channels (802.11g has three). To get that many poeple in a confined space and maintain acceptable connections and performance, the extra bandwidth will help a lot.
Good Luck
Scott
