We will be picking up a car, in Florence, and driving to our rental house in Cetona, which is southeastern Tuscany. Check in time is around 4, so we were thinking that it would be nice to take a leisurely drive and stop somewhere for a nice lunch. Looking at the map, I was thinking of taking the route through Chianti. Any suggestions on a restaurant/town to stop on the way? Any other suggestions? By the way, it will be mid-May...Thanks!

You might want to look through the Slow Travel restaurant reviews. They're organized by region, and we have quite a few for Chianti.

I have one suggestion,just an idea. You could take a drive through chianti directly to Cetona park and explore your "home town" and have lunch.RR

I agree with Robert and would add that this would be a good time, after lunch, to go to your local market and buy provisions for your first couple of days. Remember to get toilette paper, and paper towels as well.

That's a great idea, accept for the fact that we're picking up the car at around 11am, and by the time we say goodbye to friends, get out of Florence, and drive through Chianti, it will be too late for lunch in Cetona. We will stop at the supermarket, on the way, so, that's in the plan. Not to mention, this will more than likely be our only chance to stop in Chianti, as Cetona is pretty far south.

Ciao!
I have a dining guide on my site with lots of suggestions

If you are going down the superstrada towards Siena, from Firenze, there is a fantastic place a few minutes off the S. Donato exit called La Locanda di Pietracupa that I would highly recommend, from there you can wind down some through Chianti.