You might want to consider the weather you would run into in Venice; it floods often during the winter months, which might make it less attractive to you and your wife.

I am among those who think four days in Paris is not enough, but you best know what suits you and your wife. Perhaps if you would list your interests, the community could give you advice based on your interests, rather than ours. For example, some people like art, some don't, or at least don't want to spend too much time on it.

It's "to each his own", but I vote for the two cities that you want to see. We've traveled a couple of time to Europe the end of Nov.(and first of Dec.) and it was great!. Maybe? cool/cold and rainy, but not bad,(we love it that way) and even with it getting dark so early it's nice to turn in early and rest up for the next day. Flying INTO one city of your choice and then back from Paris is a great option,,,and cost not a penny more usually. It couldn't be more than a 2 hr. flight from Venice to Paris if Venice is your choice. As with any city in Europe there is usually a LOT of walking, (the best way to see things).
Actually, getting on the train in London (or Paris) and taking the channel train to Paris(or London) would be the simplest, and you would get an overview of both cities. AND, at that time of year Christmas and Holiday season are "in the air" with decorations, lights, etc (I believe)...and there is a very lovely warm feeling. London and Paris are beautiful the end of Nov, first of Dec.