Yes do make full use of a Vaporetto pass. As well as the Grand Canal Janet mentioned do take one that goes up the Giudecca and around to the Station and then around Cannaregio to get a fuller picture of life in Venice. You can give the lines that go to Tronchetto a miss unless you have an interest in cruise ships and car parks.
Venice is certainly small enough that you can get everywhere on foot as long as the water doesn't block you. Like Anna C we spent every evening walking around the area between St Marks and the Rialto, admittedly because our hotel was in that area.
If you do go to Burano, you may as well go to Torcello as well. Not a lot at Torcello and a fairly mundane walk from the Ferry stop but it is where the original Venetians came from.
You didn't want any museums, but can I put a word in for the Ca' Rezzonico. A pretty quiet museum in a very nice building, although I'm sure your guidebook will give you enough info to decide if it is your kind of thing.