It's probably not necessary to run a second DHCP server. However, based on how large your deployment is, you might want to use your infrastructure DHCP server to assign IP's to the AP's. (More of a benefit to administration than to stability.)
I would suggest that you assign static IP's to all of your AP's though. In the event that the AP loses connectivity to the controller, the AP will come up that much faster when it restarts. It also helps troubleshooting to be able to recognize a given AP by IP address in a network trace file.
To set a static IP:
1.) Click on the Wireless tab from the WLC web interface.
2.) Click on the name of the AP that you want to edit.
3.) Click on the AP Static IP checkbox.
4.) Enter the IP, mask, and gateway info where prompted.
5.) Click the Apply button.
6.) If you're changing IP information for that AP, you will have to click on the AP name again, and at the bottom of the AP config screen, click the 'Reset AP now' button. NOTE: This will restart the AP and will cause a service interruption for any clients associated to that particular AP.
Hope this helps!