Is the #E96 bus from the airport to Piraeus convenient for taking luggage to the cruiseport?
E96 will take you to the Port bus station, in the same area where the Metro station is located, which is right next to the island ferry docks and about 1/4 mile from the cruise ship docks. I'm not sure but I think there might now be a shuttle bus you can take the rest of the way if you don't want to walk. There will also be taxis, but be sure to set the price before you accept a ride.