I'm pretty sure you can change the details later. I did with my iPhone 3Gs (originally registered to my wife by accident and then to me).
A few months later I paid my dues and registered as an iPhone application developer and for some reason I'm still called "Vicky" on my profile!
I cant remember what I did with the iPhone. She got my old iPhone when I got the 3GS. I might register this anyway. Doesnt really matter. As long as I wipe it when I get mine and sync it with her iTunes as a new iPad. Anyway, best in my name as if it goes wrong it's me who takes it back.