It seems like a bit of a long time in CT. Besides hiking the towns, there's not much to do. You can see each town in a couple of hours each, for the most part. I would personally rather spend one of those days in Florence. Over 2 trips I've spent a total of 8 days or so in Florence and I still can't wait til I can go back (And I don't like art!). But that's just me. Certainly nothing wrong with saving Tuscany for a later trip, that's what I did, and I combined it with Cinque Terre. In 14 days on my first trip, I did 4 in venice, 5 each in Florence (took a daytrip to Siena via bus), and 5 in Rome. I thought that was a perfect length of time in each place, though I still felt like I would have loved more! While I totally understand the desire for a "small town" experience, I don't think you'll get it in Cinque Terre, which is completely overrun with tourists IMO (and I was there in October, I guess September would be even worse), and where English is basically the first language. If you want to go there to hike, to eat seafood, or to see the natural beauty of these little villages, then yes go ahead for a couple nights because it truly is a beautiful and unique place, but what you're looking for is just a small town experience, then in my personal opinion, you are better off in a town outside one of the big three for a night or two. As for Florence on a weekend, you'll be fine. I've been there twice on Sunday (one of those being a major holiday, no less), and I have never had trouble finding good (even not-so-touristy) restaurants and plenty of things to do. Otherwise, September is a great time I think! The weather was pretty much perfect when I was there!