Todi as our base for 7 days; drive to the towns around or plan on trains?

Glad to see you are visiting Todi, one of my favorite places.

If you click on the British flag icon at the Trenitalia site, the page will translate into English. I don't think mid-June to December schedules have been loaded yet, but your dates should show.

Trains and even buses to/from Todi are not particularly convenient, I would plan on driving to other towns. When Roberto sees this post, he can tell you where to park in Florence without violating ZTLs. Getting in and out of Orvieto can be a challenge as well.

As for Florence as an overnight, definitely.

Todi has a well-located public lot with a bus shuttle into the old town.

Go to www.trenitalia.com
For English language you need to click on the British Flag icon. That is true on many websites, not only this one for the trains.
The trains that travel from Orvieto to Florence (Firenze Santa Maria Novella station) are mostly "Regional" trains (like commuter trains). The schedules are published weekly, therefore to see the schedule you need to enter a date in the next 7 days. Timetables are more or less the same in June.
For time early in the morning, just enter 00 under Time. It will show all trains from the first one departing in the morning. For the return time do the same, enter a time in the evening and it will show all trains after that time.
Spending a night or two in Florence would be ideal, as Florence has a lot to show, but that is up to you. If you decide to spend nights in Florence, I suggest you return the car when you arrive, then you can return back to Rome by train.

The drive from Todi to Florence is just over 2 hours. I would recommend to park at Porta Romana parking lot, or Piazzale Michelangelo.
The drive to Orvieto + train combination will take you at least 3 hours each way. The advantage of the train is that you don't have to drive, except for the 50 min from Todi to Orvieto (and vice versa).
Florence is a bit far from Todi, so if you can do Florence after your Todi stay (maybe for 2 nights) it would be best.

So to Roberto's post. It looks like we can drive to a location outside of Florence and park the car Porta Romana or Piazzale Michelangelo. From there would we try to find public transportation? It might save some on our travel time if we drive rather than try to do the train and drive. Yes we would be a long day so we just have to decide if we want to spend 4-6 hours traveling on one day or do the 3 hours on 1 day and overnight in Florence and return back to Todi for the rest of our time. Two in our group want to go to Florence but I realize there is some distance. It feels like there is enough to do each day in Umbria and still have time to relax and enjoy our time at the house we are staying at in Todi.
We plan to return to Italy again. This is our first trip and we know not to pack too much in to the days so that we have time to enjoy what we can experience.

Pjazzale di Porta Romana or Piazzale Michelangelo are not outside of Florence. They are at the edge of the historical center. You can walk from Porta Romana to all sights in the city center.

There is also another solution which may be preferable to all of the above, which is:

Drive from Todi to Terontola train station (80km, all freeway) in less than one hour.
Take a train from there to Florence (one or two every hour, less than 1,5 hr trip).
The train station in Florence is in the city center.

The above solution is just as fast as driving all the way once you allow for unpredictable traffic in Florence, getting lost driving within Florence, and finding parking. Check out the drive and parking at Terontola on a day you take a day trip drive to Cortona (I'm sure you'll visit there from Todi), since you have to drive through Terontola to get to Cortona.

For train schedules check:
www.trenitalia.com

Use Google Maps to plot trip from Todi to your final destination (whichever might be).

I had never heard of Todi and have been looking at sites regarding this city. It really looks like a good place to visit. BUT I have a little difficulty walking and it seems that everything is either uphill or downhill, up stairs of downstairs. Is this correct?

Nanc1930, there are plenty of hills in Todi, but the main piazze (three of them, practically adjoining) of the old city are pretty flat. I finally got to use my trekking pole last year (my hotel was dowwwnnnnn a hill) and had no difficulty; there were a number of places to stop (I did stop on the first day). But there are several hotels around the corners from the main piazza. Also near my hotel was a bus stop that would first go down to the lowest part of the city, past the gates and the parking garage, and then up to the main piazza.

Thanks. It sure is tempting. We will be training, tho, and I think this time it will take too much of our time. Now, if we had a car like I did on the first time I went alone, that's another story :)))