Hi haydockman,
For the luggage, a small soft sided bag/holdall would be suitable, one traveller last week had a small, square, soft-sided suitcase that turned into a rucksack.
In terms of currency, for the extension, we'd recommend Peruvian Sol, you can easily exchange US dollars in Lima, Cuzco or Puno before you head off on your adventure.
I'm just putting together a hints and tips from my own Peruvian adventure last week which may help with some of your preparations.
Kindest regards,
Julia