Can you facetime ipad to another ipad?

Yes, but both iPads need to be on wifi (as FaceTime only works over wifi) :

When calling someone using an iPad 2, iPod touch, or FaceTime for Mac: Use the email address designated for FaceTime of the person you are calling.

On iPad 2, iPod touch, and FaceTime for Mac, you need to add a person as a contact using the FaceTime or Contacts app before you can call them.

That is what this page says - it says to use the phone number to contact somebody on an iPhone. As I've got the first gen iPad it's not something that I'm able to use on it.

Yes as long both iPads are iPad 2's and have a wi fi connection

Correct