We did a private tour with Rome Cabs (actually - Stefano Rome Tours) that combined both several years ago. It was perfect as we, like the OP, had done Rome pre-cruise and didn't wanted something different before heading the the airport hotel for the night for a flight home the next day. They picked us up at the port, took us, and our cruise luggage, to both Orvieto, Civita and a couple other places before returning us back to FCO that evening. Great day!