Francine,
There are cars lined up right at the docks for rental. You will be there two days each port. I think Eurocar was at both places. The cars are little tiny cars (Smart Car or Peugeot type)with stick shifts. Or open Dune Buggies too. We did not rent them - we did not vfeel that we needed a car. You can also rent them through the excurision desk - they will book it for you.