I know that for computers, AppleCare is shipped because they still send out the paperwork documenting that AppleCare has been set up for the computer (listing the hardware along with its serial number).
They may very well do the same thing with iPads. Of course, doing so would require that the serial number of the iPad be available, and they're not yet for 3G units, so it's possible that those AppleCare orders would get codes to use online to activate the AppleCare after the iPads arrive at their new homes.