There are some really cosy and romantic B&Bs in Venice. But if you are going in the summer, Venice is not exactly a quiet place to visit.
You will be hard pressed to find a quiet spot outside of where you are staying. Even in the winter it is a pretty popular destination. about 10 years ago
Venice itself is just lovely and romantic. Definitely agree with NikoRoberts and say you have to go out of season. I have been in both February and December and whilst its busy, its not that bad.
Take your time to just wander around. Venice is a walking city. Each day we would decide where our end objective was, say St Marks Square, and then spend time just meandering around to get there.
You will find hidden gems at every turn - a gargoyle face used as a bell push, or a tiny recess in a wall which is a shrine to a saint. Look up, look down, just keep looking.
The museums and the architecture are amazing. I love the shops.
I simply adore Venice. about 10 years ago