Andrea, I also planned to go to Orvieto as a day trip, but changed my plans to spend a night there. Loved it! Early morning and then late afternoon and evening are wonderful times, quiet, sometimes very misty, and without the day trippers and bus groups, can be the best times. The intricate and colorful facade of the Duomo is magnificent, especially in the late afternoon of a sunny day, and in the evening when it is illuminated. Inside is the Signorelli Chapel, which if I remember correctly, was an inspiration for Michelangelo's Sistine Chapel. Looking at the Duomo, one part of the Dumo Museum is off to the right side and behind, and in there you go eyeball-to-eyeball with some ancient mosaics, where you appreciate the intricacy of tiny pieces in the works. I did not do any of the underground stuff, but have heard great reports. Lots of small stone streets, with many interesting shops of ceramics, olive wood, wines, etc. Good small restaurants, which tend to be closed one week night, but different nights for different places. Helpful TI office in front of the Duomo. Your kids will like the quick funicular which takes you from the train station up to the olde city, so will you I expect. Neat ride. You know the stamina of your group, but I would encourage you to stay late-ish, to walk the town late In the day and have a nice dinner in Orvieto, a totally different experience than most of Rome. One nice part of visiting Orvieto as a day trip is that you wouldn't have to worry about having baggage with you. If you need me to show you around Orvieto, just send me a ticket!
