I'm not planning on doing anything until we get there either. I just don't plan on spending that much cash. I'll probably get a little at the Guest Services before disembarking the first time and then maybe find an ATM machine if I need more. I'll credit card any larger purchase and just eat the 3% fee.
I just got done order Euros for our trip. We went back and forth about how much cash we would need and what to do about the balance we had left. And decided the following:
We are planning on about $150 Euros per port to cover food, drinks, souveniers (lots of family to buy for) and possible taxi fares, etc.
We figured we would know by Gibralter if we are going to use the balance of Euros that we have, and figured that if it looks like we will have a larger balance of cash left over than we will actually need, we will use it to pay part of our stateroom bill and/or since we usually tip more than the standard amount, we will use the extra Euros to tip some of the staff . That will also give them some ready Euros to use at all the other ports.
This solves the problem of having enough cash in the ports and not leaving us with a bunch of Euros we will have to convert when we get back to the states.