Currency exchange establishments in Europe will no longer accept the old US currency. They want ONLY the new bills with the large pictures. They are afraid of counterfeit. So-- exchange your old bills for new ones at your bank before you sail.
Not a problem since (1) you can exchange currency aboard ship, either at the Pursor's Desk or using machines provided for that purpose, and (2) you can make major purchases with credit cards. MasterCard and Visa are widely welcome.