We will be arriving in Venice at 6:40 pm on May 2nd which is a Saturday. What can you do in Venice at night?
For one thing, you're in time for dinner. Dinner begins about 8:00pm or a bit before. It's great to roam around the side streets only to discover wonderful local restaurants.
You're lucky because evening is one of the best times to be in Venice. You'll avoid the throngs of daytrippers that have already vacated the city and gone home for the evening...wherever "home" is for them.
Gongola rides, wine tasting, and just strolling around is more than enough excitement on your first day!
Make sure that you go down to San Marco's square and see the dueling orchestras that perform outside the high-priced cafes. If you grab a seat you are expected to buy something (and it will be expensive) but standing is free and the music is unbelievable... they play everything from classical to more modern (the rendition of "I will survive" was memorable).
Venice at night is magical and was my wife's favorite time there. Actually, arriving at the time of the day you are is not a bad thing. Check into your room and stroll on over to St. Mark's square, relax and listen to the Orchestras. If you are a Sound of Music fan one of the groups will play a medley of songs from the movie and folks sing along. Or try to anyway. :)
What a wonderful time to arrive! You can cruise the Grand Canal on the slow boat and watch the sun go down as you meander down to your hotel. I'll never forget doing that last fall--it was magical to see the big round October moon rising over the palaces lining the canal. Then, after a leisurely dinner, dancing in St. Marks to the dueling orchestras. A cherished memory! Also you save euros not taking the speed boat into town or sitting at those little tables, sipping those very expensive drinks. The nights in Venice were a highlight of our trip to Italy.
Evening in Venice is magical, as everyone so far has assured you. But get your dinner as soon as possible. Venice is not a late night place.