Sure, extra travel during a limited stay is not good. In fact, I hate it. But you did raise the question. You may already have considered a train. Some of them really haul ass, and total, end-to-end time might actually be less than dealing with airports and attending commutes, if you try it at all. My wife and I like to spread out and get comfortable on the train, and we take our picnic stuff aboard. The first time I visited Venice was on a spur-of-the-moment "side trip" from Austria, where we had gone... skiing. It was too rushed, of course... but Venice was/is - after all - Venice; and Paris remains Paris.