Create or use an existing guest network for the iPad
Q: My boss bought an Apple iPad and wants to connect it to the Wi-Fi system at work. Should I let him?
A: Kind of. You can't say no, but you don't want an unmanaged device on your corporate wireless network. So, you should suggest a compromise.
Create or use an existing guest network for the iPad. Ensure the guest network has Internet access without secondary authentication. Configure the iPad to use that as its preferred network. For email and calendar access, configure the iPad to point to your Internet-facing servers, just like laptop and home workers. Now you've got a fully functioning iPad that's physically at work but isolated from the internal corporate network.