Just to add my two cents advise on data card transfer:
a) Yes it is better to take a 2 gb camera card as it is easier to edit than a 4 gb card
b) Yes carrying a few sets of lithium battery hold more charge than the normal throwaway batteries and is easier than carrying a charger, the Spanish sockets need an adapter to suit the two pin flat plugs used in NZ and OZ if you bring a charger. We found that using the video capability of our camera chewed up a lot of power, but battery replacements could be done on the go.
c) We carried cheap flash drives and a card reader, these little gadgets allowed us to transfer the day's photos, videos, and audio notes, from the delicate camera cards into the flash drives (pen drives) through the USB connection on the computer whilst we were on the internet. The transfers can be done simultaneously whilst emails are read and replied. We also edited the photos in the flash drives at leisure so that they could fit into a CD when an opportunity arose.
d) Modern computers have inbuilt card readers and CD/DVD writer, so perhaps in the not too distant future you can transfer, edit, save, and burn CD's without using a separate tiny card reader and looking for a CD burning shop during the Camino. I am hopeful of this upgrading of computers as Spain's tech-savvy is second to none.
Hope this help
Kwaheri