Rome in 4 days

Looks good to me. I would move the Pantheon to Day 3 as it sits well walking from Trevi Fountain, to Pantheon, to Piazza Navonna. Glenn

There is nothing wrong with the way you carved up things. The Vatican can run from a couple of hours to half day if the museum and chapel is included. Except for the Coliseum, the others are relatively quick hits or just a slow stroll through. And same for day 3. All are kind of walk bys.

Looks very good to me. On Day 1, you can dine in the Trastevere area. It's a charming medieval neighborhood. I also think you can see Villa Borghese on the morning of Day 3. Trevi Fountain, Spanish Steps, Piazza Navona and Campo Dei Fiori can be done in an evening stroll. They're within walking distance. Did you make sure the museums are open on the days you're visiting?
The Vatican museum closes on Sunday.

It looks good to me! I am not sure where your hotel is...or how late you stay out...but I LOVED walking to the Colosseum...and Trevi fountain during the early AM and then again late at night...such a different view and both very amazing! Silly detail maybe...but I still remember the difference... :) Have a wonderful trip!

You can easily do that in three days, I think we did it in an aggressive 1.5 days. I would suggest that you try to see many of the sights in the day and night. Our Airbrnb host suggested that to us, and he was right that Rome is a different place by night. We also did a night tour of the Colosseum.

M&S, I'm excited for you too. When is the trip? For your 3.5 days, what day of the week are you arriving and leaving Rome?

Glen is correct. Move the Pantheon to Day 3 -- it's closer to those sites.
Make a reservation for Borghese museum -- and be 1/2 hour early for your appointed time. The Pantheon and Forum are pretty rugged walking, FYI, and I had trouble finding resting places - so you may just want to do a drive by because you have these walking issues too. All of these days will not only "allow" but require strolling -- and of course with the exception of the Trevi - which is busy all the time, there are plenty of places to sit and relax and have a drink or lunch or dinner or both! You can Add the Trastevere area to the end of Day 3 - it's across the river (I believe) someone correct me if I'm wrong, and the walk across the bridge is beautiful and a scene you've seen thousands of times! Don't forget the beautiful Church in Trastevere -- St. Maria. I think it's the oldest in the city, and the first named after Mary after the legalization of Christianity. I'm excited for you too!!! Happy Travels!

Nigel, Here's our trip: 9/28 - 10/1 - Venice 10/1 - 10/5 - Tuscany (Barga) & Florence 10/5 - 10/7 - Sorrento
10/7 - 10/11 - Rome (fly out on 10/11) We are in Rome on Monday and leaving on Friday. Any thoughts on a inexpensive (cheap!) place to eat near the Spanish Steps or Campo Dei Fiori for Dinner? Thanks! Mike & Sherry

Michael and Sherry thanks for sharing! I am so happy for you guys and wish you a wonderful trip and life together!

M&S - Our favorite Roman trattoria is a a short walk from Piazza Navona, Antica Taverna on via Monte Giordano. Google Map it. Very Italian, frequented by locals, and quite inexpensive, esp for Rome. Enjoy!

Thank you Laurel and everyone
much appreciated.