We went on a Tuesday to the Accademia. I would not recommendb being there on that day because it is the busiest day after being closed on Monday. We had to wait for over an hour to enter, even with "skip the line" tickets. Not Viator's fault, just crowded, even in Oct. The tours were good. Very knowledgeable guides. Sometimes difficult to hear well, even with the audio devices, so just try to stay close to the guide and listen w/o the device. Overall a good experience. A lot of art in one day, but you have a break between the two tours for lunch, etc.
A good overview of San Marcos, Venice. Did the walking tour in the late morning, starting near St. Mark's Piazza, and ending at the Rialto Bridge. Sometimes hard to hear with the audio devices. Good excercise. Pretty informative. The best part was the Grand Canal boat tour later that day. I highly recommend that you return for that in the afternoon!! That was amazing. There were not as many people as there were for the walking part of the tour, their loss if they missed it, but better for those that did return for it, as it was not as crowded as it could have been.