If you can get your Euros before you depart it would be a good idea, not sure about Stateside banks, but for Europeans we will often find that our cards are blocked to avoid theft/fraud unless we advise the card issuer in advance.
If you can't get any before you fly, then still try the EU banks, you will always get your card back, or as a last resort (as their rates are usually bad) buy them on the ship, or their onboard ATM.
As for security, I wouldn't expect any issues, I don't believe any ships have been diverted yet, and the situation is highly unlikely to get any worse (imho).
One word on food & drink is to avoid salad & even ice cubes in eastern Med ports, as they are more likely to contain bacteria which could cause upset stomaches & spoil your experience.
Well on that depressing note, I'll still wish you a lovely vacation,