Restaurants in Venice are more expensive than what you'll find in the rest of Italy. We had a superb birthday dinner for 8 at Fiaschetteria Toscana in Venice. It is a small, traditional place that has been owned by the same woman, a good friend of Marcella Hazan, for years. Try for a reservation at 7:30 for the best selection of fresh seafood. ( Venice is known as an early-eating town.) I believe it is closed on Mondays.
Corte Sconta & Osteria di Santa Marina are very good and mid-range in price. Corte Sconta has seating in a lovely outdoor courtyard, but that is weather-dependent. Closed Sundays.
Lineadombra is the best of Venice's (few) new & modern restaurants. Very good, but not traditional in any way.
If you feel you must visit Harry's Dolci, across the lagoon, skip dinner there and go for dessert (the torta cioccolata!).