We went on our first cruise last September and we also went to Norway
We took some Norwegian currency but only spent about £40 on a few souvenirs. The shops do take credit cards but I thought we might stop for a coffee, but we found that we always went back to the ship for lunch.
Enjoy your cruise but bear in mind you will be hooked on cruising.
Since our first cruise we went again in April and have 3 more booked.
The Saga Experience is very addictive.