We used Kefalonia Taxi Service and were very happy with our experience for a group of 6. It was 250 euros for 4 hours. We added a 5th hour for 50 euros more. We had a comfortable van with a very friendly guide and customized the visit to what we wanted. Before we were picked up, we walked along the water in Argostoli and had great fun spotting the sea turtles. We must have seen at least a dozen! When we went to Melissani Lake, it was packed with big tour buses, so we switched around our itinerary and came back a little bit later and had the place to ourselves, which was magical! We stopped at the very silly Odysseus Land for the kids in the group. Some of us wanted a beach, some just wanted to relax at a cafe, so we went to the amazingly beautiful Antisamos Beach which had both. Those who wanted to swam, the rest stayed ashore eating and lounging on the comfy chairs. Everyone called it their favorite stop on the cruise because of how relaxed it was.