I have not been on an
ABD trip yet but DH and I did go to Italy 2 years ago on our own for a lengthy trip seeing most of the country. We went to Milan, Rome, Venice, Florence, Capri, Pompeii, Amalfi Coast, Pisa, etc.
Having been on that trip, I convinced my DBF and her DH to book the ABD tour that is going to Rome, Florence, Venice. I think it offers the best of the best for a first trip to Italy and I thought the price was very good compared to what we spent on our own. Personally, I could not imagine going to Italy and not seeing the Vatican so that would be the first priority for me (and this particular ABD tour does take you there and inside St. Peter's). The second thing we loved was Venice, at least once in a lifetime to see that city. The various tours that ABD offers will give you a pretty good selection of interesting things to see.
Although we did enjoy the Amalfi coast and Pompeii, etc. I did not LOVE LOVE LOVE it the way I did Rome and Venice. And I would not go to Milan or Pisa again. I'm actually kind of sorry that ABD wasn't around then because it seems like this one would be the perfect trip.
As far as booking, many of us have booked already because we wanted the early booking discount (I booked Nights and Lights in August). However, there are still spots available. My DBF and her DH just recently booked their Italy trip for next year and were able to get their first choice of weeks.
I don't know if this helps you but I'm sure that your family will love that 3 city tour.