If you want to make your trip more exciting, you can go to Venice by car. This is what I did. Keep calm, there are parking lots. There is an artificial island with 4000 parking places and a fully automated train without a pilot which will take you to the place where you can get some food. I guess it was hard, but they figured it out.
If you want to mix with about half a million people, San Marco square is the place to go. There is a buzzing sound all over the place. It is a buzzing in all the languages of the tower of Babylon. You need a lot of nerve in this crowded
place. You may have to wait for an hour or two before you get to see the cathedrals and the palaces. There are queues. Huge ones.
Therefore, you'd better buy yourself a captain's peak-hat as a souvenir and slip into the narrow side-streets where the real Venice is. And the town is really wonderful. Old buildings, gondolas, seafood ... just as everyone imagines it, I guess.
Go before it has sunk.