You can get a cash advance of $400 per person per week on Radisson ships. They can give this to you in Euros or Dollars. Since these are billed as purchases, we actually earn airline miles on these transactions.
Unless you need travelers checks for pre-cruise, there is no need to take them. In addition, we found that ATMs in Europe were great and not too expensive. We also order around $100 in foreign currency from our local bank prior to departure just so we don't have to worry about it when we first arrive; airports are the worst place for changing money.
As for purchases in shops overseas, we really try to use credit cards; just in case something happens (see past posts re: Malta Glass Factory :( ).
Have a great cruise!