First time trip to Paris with children. Thinking that the Left Bank will be the most interesting for us. Possible streets where possible accommodation is, are Rue Vaneau, Rue Jacob and Rue de la Montagne Ste Genevieve. Does anyone know which street is the best location for checking out the sights and also which is the busiest street in terms of traffic? We would prefer to sleep at night so don't want a heavy traffic area. Looking for some urgent advice. Help please!

Rue de la Montagne Ste. Geneviève is fairly narrow, so that no heavy traffic will drive by. But it is loaded with restaurants with outdoor eating areas, which might produce noise in the evening. Rue Vaneau is in the ministerial district of Paris, so is likely to be quieter in the evening. Rue Jacob is narrow and hence fairly quiet. Rue Jacob might be the best bet--close to the Seine and near the Musée d'Orsay

rue Jacob is a small one way street in a perfect location between Blvd St Germain and the Seine. You can get anywhere easily from there.
It is , in it's way, quiet. All rooms on the courtyard in hotels tend to be more quiet. Avoid rooms that overlook the street.
You are just a block or two from some nice large cafes where you can have breakfast or lunch ( Deux Magots).You are not far from the D'Orsay, Louvre or the Luxembourg Gardens.
so rue Jacob gets my vote ~

I don't think any of them would be super-noisy, but suspect Vaneau would be the quietest. The other two are very small streets (I thought rue Jacob was maybe pedestrian-only, but guess not from above folks), but that often makes them noisier, although not lots of heavy traffic noise. It's just in those very narrow streets, you can really get a lot of street noise from the people walking by and talking/shouting, whatever.

For quiet, I'd choose Vaneau or try to get a room off the street. I think the other two might be slightly more convenient locaitons, though, as parts of Vaneau are not that close to a metro and there is not as much right around there (cafes, etc). So, it's a tradeoff--convenience vs. quiet. If that hotel on Vaneau is near Vaneau metro stop, that is a convenient point as two lines cross there.

None of them are bad locations for tourists, they are right in central Paris.

Thanks everyone. Your comments are really helpful - I can live with pedestrian noise as opposed to traffic, I think that probably adds to the atmosphere of being in Paris!! So I will probably go for Rue Jacob on that basis.