Log into the dev portal at
iPhone Dev Center
Add the devices.
Create your adhoc distribution provisioning profile.
Add the device to the adhoc provisioning profile.
Download the adhoc provisioning file and install in Xcode.
Create an Adhoc configuration in Xcode.
Build your app for Adhoc distribution.
No new app ids required.
This is all documented in greater detail on the dev portal. Just read the docs.