I can't answer your question directly, but I would love to share our experience in Venice last year.
Our cruise ended in Venice and we spent an extra night (on our own). We booked a very early flight and were forced to take a water taxi from our Hotel (Regina Europa at the mouth of the Grand Canal) to the airport. We had all our cruise luggage and purchases with us. The water taxi cost -- 90 Euros plus tip. Then we needed a taxi from the water dock to the airport terminal -- another 25 Euros plus tip. Then we needed another porter to drag our luggage from the street to the check-in (another tip).
We were so glad to leave!! Venice is beautiful, but the bridges, water taxis, and number of tourists gets stale after a few days.
Enjoy your stay in Venice. Don't miss a trip to the Murano island glass factories.