We just got back on Friday, and since members here were so helpful about answering my questions, I wanted to give a quick review of our trip, including some of the things I was worried about.
First of all, we ended up transferring our phones to T-Mobile, and bought their international package for 10 days, and it worked great. I would definitely recommend it.
Next, we had no problems using our credit cards anywhere. When we tried to get Euros at an ATM, one bank card (Regions) was declined, but the other (5/3) worked fine.
We converted $200 and that was plenty, only having to buy some chocolates at Schipol on our way home.
The cruise itself was fabulous, and we would definitely recommend AMA Waterways. It is definitely upscale, especially the food.