Kathleen-
We arrived in Venice in the afternoon and took the gondola ride that evening. In the morning, we went on a canal boat ride which took us through the main areas, some off the beaten tracks in the non-tourist areas of the city. The ship sailed in the afternoon and we had no more time. However, the cruise out of Venice is something special too.
I envy you, I'd love to revisit every port again. It is a fantastic itinerary.
Maggie