Jean,
Yes, we purchased the ticket already. I talked about that on a separate post. I had initially planned to fly into Milan and home from Rome but found the flight service home from Rome was awful. Maybe the better flight options were already booked but I was getting 25 hours from Rome to Dulles, with an overnight layover (9 or 10 pm until the morning). I wouldn't mind a long enough layover for a look around, but overnight just means either getting a hotel room (without actually visiting the city) or suffering in the airport.
Surprisingly, Venice has a ton of good options from Dulles (Lufthansa, SAS, Swiss Air, Air France, Turkish Air, TAP, plus U.S. carriers). Our flights, on Lufthansa, have a two-hour layover, each way, in Munich.
I was thinking Verona as my backup. If we go to Bolzano, we'd probably make a day-stop in Verona to see the arena and center.