If its a med cruise, just take euros. I always order mine from Travelex and collect them at the departure airport. Much better rate than High St Travel Agencies.
We find Post Office has best rates and just take euros...travellers cheques are a bit old fashioned now, not many people use them.
Don't forget there's a 'Hole in the Wall' in every port you stop at. It's hardly
worth 'buying' too many Euro's before you leave the UK.