Look up your states DMV, and they'll list what is needed. A SS card should not be needed.
As far as power of attorney, I downloaded a form for my Dad, it was $15 and filled in all the blanks, then you'll need it notarized.
Still, if he has his address on something and the birth cert you should be OK.
Or even better, if he has suspended license thats still in the system they can see his pic.
Seems these days its easier to have your identity stolen than to prove your own!