
San Giorgio Maggiore
The Campanile in Piazza San Marco and the tower at San Giorgio Maggiore (vaporetto: San Giorgio) both give spectacular views over Venice and the lagoon. Remember to take some change for the telescopes, or better still bring your own binoculars. If you get your timing right, you can experience the ringing of the Campanile bells at close quarters!
This has to be booked in advance at the Doge's Palace information desk (041 522 4951) - buy a ticket (€12.50 per person) to go on an English speaking tour. You will meet in the courtyard to start your tour. It takes you into rooms that are not included in the general admission price and tells you stories and tales of what happened, for example the escape and imprisonment of Casanova. The tour skips the main halls in the palace but finishes in the palace so one can visit after the tour has ended.
Calle dei Furlani, Castello. A good "art" choice for young children. Carpaccio's scenes are a lot like fairy tales, with dragons, knights and princesses.
On Calle degli Albanesi, east of Piazza San Marco; 9am - 7pm, closed winter and Tuesdays. This has lagoon fish and species from the Mediterranean, Adriatic and tropical waters.

Rialto fish market
Rialto, Tuesday - Saturday mornings. Children are fascinated by the huge variety of sea creatures on offer at the market. Best to get there early!
Campo San Biasio, near Arsenale (vaporetto: Arsenale). This is great for children of all ages, with model boats and guns.
The public gardens at the eastern end of Venice (vaporetto No 1: Giardini) are a good place to play. Most Italian children play in the local campi, and it is rare to walk through Campo Santa Maria Formosa or Campo San Polo without having to dodge round a game of football.