Hi Rebecca,
I walked the Camino Aragones in early September. At Arres, I looked at the signing-in book for pilgrims and found that even over the Christmas period last year and early in the New Year, there were walkers. So it seems that it is very do-able in winter.
Apart from Somport down to Canfranc, which can be a little steep, it isn't difficult and from there on it is a gentle downward/flat route to Obanos. Only out of Ruesta and Sanguesa were there any hills that took a little more effort.
I'm going to post info about how to get to Somport via bus/train if that is your starting point and some general info about the route.
But, sorry, no, I don't have any free time over the Christmas period!
Nic.