[Hondaracer]

Can't speak to Venice or Rome but Florence is gonna be stupid with a stroller.

Almost everywhere you go has stairs, cobble stones, etc. public transit there is useless because everywhere you go for the most part are pedestrian only zones or streets where busses etc do not operate. There is no big bus tour or any thing similar because you can't drive in a loop to the major attractions. Renting a car would be even worse. Buy the Firenze pass in Florence to get into all the attractions and skip the lines. If you don't and think you're gonna wait in line with a 9 month old for 2 hours to see the David, I'd say have fun with that.

No offense but going to those places with a 9 mont old sounds like a nightmare to me.