With kids, Basilica di Santa Maria della Salute works.
Longhena's octagonal white domed Salute is the silhouette that crowns every Grand Canal photo, built in thanks for deliverance from plague; inside, the sacristy holds Titian and Tintoretto canvases. Standing on its steps where the canal meets the basin is one of Venice's free pleasures. The catch: the main church is free but plain-ish for its fame, with the real art behind a small-fee sacristy door.