Rental Car Logistics

Take the 70 minute train ride from Rome Termini up to Orvieto and pick the car up from Hertz. They're 100 yards from the front door of the train station--across the street.
Go to AutoEurope.com to compare prices with Hertz.com. You can join Hertz' Gold Club (for free) to get discounts.
It's maybe 90 minutes to Siena and a little over 2 hrs. to Florence from Orvieto.

I'd also suggest spending the night in Orvieto as it's a really nice hill town with good hotels and B&B's.

I concur with the advice to rent from the airport if you will be departing from there. I also suggest, according to your departure time, that you consider staying at an airport hotel the night before. That's what we did. That gave me plenty of time to turn in the car. The hotel (Hilton) had a free shuttle into town and we spent a wonderful evening in Rome. Of course this might be a bigger chore with an 18 month old.

Needless to say, Tuscany is magical. However, a car is a burden in Florence. I suggest you stay in a small town and if your plans include Florence, take the bus into town.

With the 18 month old, I would avoid the transfers and just rent in Rome itself. Depending on how long you're renting for, consider buying a car seat before you rent and save.

Are you also flying out of Rome. Possible to rearrange so you get the car when you land head right to Tuscany and then stay in Rome at the end instead of beginning of the trip?
Having traveled with a young baby/toddler a few times I know the extra stuff and burden that it can be and public transportation often becomes difficult to manage.

For our recent trip we purchased a car seat since it was cheaper to do that than rent and then I just left it inside the rental car when we dropped off the car, they didn't mind and gave us piece of mind to know the car seat we were getting was a good one. Would have not left it behind but the end of our trip was in cities and we did not have the car so lugging around a car seat would have been no fun. It is worth noting that most US car seats technically cannot legally be used in Europe though it is not enforced.

Nicole,

If you haven't driven in Italy before, you'll need to be aware of a few potentially expensive "caveats" on driving there. To begin with, each driver listed on the rental form will require the compulsory International Driver's Permit, which is used in conjunction with your home D.L. These are easily obtained at any AAA office for a small charge and are valid for one year.

You'll also need to do some research on the dreaded ZTL (limited traffic) areas, as hefty fines will result each time you pass through one of these. Many towns have some form of ZTL area, either enforced by a camera of a "cop on the beat". Do NOT drive in Florence as the main part of the city is just about saturated with automated ZTL cameras. There are also speed cameras and other traps to be aware of.

Don't underestimate the matter of ZTL (or any other) fines. I recently received a note from someone who received two ZTL tickets and these were eventually turned over to a North American-based collection agency. By the time the dust had settled, this individual had paid about $700 to settle the matter.

Completely agree with Ken on the pitfalls. I will say driving in Tuscany on the back roads and over the hill tops is a wonderful experience.

Yes, we have no intention of driving while in Rome. I was thinking that it would be easier to fight jet lag in Rome, where if we get up early, we won't be bothering others in our hotel, like we would in an agritourismo. We can get out early and stroll and enjoy the city, rather than trying to keep an 18 month old quiet while in the countryside. I also would like to come home not feeling absolutely exhausted, and I think that at the end of our 2 week vacation, we may be too exhausted to truly enjoy Rome!!!

After reading all the horror stories before we went to Italy last December, I had started to doubt whether renting a car was a good idea. I weighed that against my good driving record and felt that I was reasonably intelligent and could understand and follow the traffic laws. It turned out that I was right. I stuck to a few basic rules starting with don't drive in Rome and don't drive in Florence. In all the smaller towns, especially hill towns like Radda, San Gimignano and Volterra the ZTL's are clearly marked and easily avoided. Also, speed limit signs are easy to read and easy to obey. Every once in a while there would be a local who wanted to go faster. I just either pulled out (it was a good excuse to stop and admire the scenery) or gave them room to pass.

I don't know how much you travel to places were jet lag may be an issue. I've done three trips this year and I'm about to go on a business trip to Hawaii. I've found the best way to handle it is to push through and immediately adapt to the new time. The first day or two can be tough, but you acclimate faster. Of course, I haven't been toting around an 18 month old. Depending on their nap schedule, they may actually have an easier time adapting.

Finally, if you are anticipating being exhausted at the end of your trip, I suggest you rethink your activity schedule. There's always the temptation to cram every single waking moment with sightseeing. No matter how hard you try, you won't be able to see it all. Aim for quality instead of quantity. Be flexible. We had sketched in a day trip to Pisa and Lucca as well as a stop at Assisi on the way back to Rome. We realized that although we could have done it, the day would have been brutal. We opted to explore smaller nearby towns instead. They were off the normal tourist path and we had a great time exploring at a slower pace. We also interacted with the residents more than we would have if our goal was to check off another "must see" attraction.

Nicole, I think you will find after a week or more in the Tuscan countryside even if you keep a fairly busy schedule you will be quite relaxed by the end and not at all exhausted. It is a laid back lifestyle kind of place and will rub off on you I am certain.

Your point about Rome at the end is valid in one respect though, we just returned and did Paris at the end. Trip wise it worked out well and got to Paris relaxed but returned home very tired. Had we started with Paris we likely would have returned home less worn out since the last days of the trip were our most taxing. I also see your point that the first couple of nights may be the toughest for your child to go to bed. Given that Italians tend to adore and fawn over babies I am not sure though if the owner of an agristristimo in the countryside would not be more understanding than fellow tourists in a hotel setting in Rome.

You have to weigh that against the logistical factors. Try to stay awake and be outside your first day will help get you on local time and overcome jetlag faster. If your baby at 18 months traveling is like ours was (we also took a trip when she was 18 months) than having a rental car where napping is easy was usually the best situation. Most kids at that age fall asleep in the car easier than most anywhere else. It is hard to pack light with a baby so the car becomes more convenient than if traveling as a couple.

If you pick up your rental car near Tiburtino you can very quickly get on the autostrada headed to Tuscany. It's probably about a 30 euro taxi ride from central Rome.