The best thing is to call Cisco Sales rep for your area and he will provide you with all the details.
Briefly, either you get someone for site survey and he/she will let you know how many APs will be required for each floor as per number of users. You can also get some idea about range of AP if you have an AP installed and working.
You should buy APs like 1131/1232/1242 which are 802.11i compliant, so that if you want to go with this new standard from IEEE, you should have right equipment already installed.
If you will buy laptops with built in wireless adapters, just make sure that those support standards like WPA/WPA2/802.11i. Mostly these new cards support WPA/WPA2 but require atleast Windows XP service pack 1 for WPA and SP2 for WPA2 with a hot fix. If you go with Cisco Client adapters, try to get ones supporting the new 802.11 i too and software comes along with it.
You can use ACS server for authentication and reporting.
I hope this helps.