Planning my first trip to Italy in early August (25th wedding anniversary). It will be family of 4 (all adults)

Arrival and Departure dates in Italy are pretty firm but the dates in each city are flexible. Plan on getting between Rome/Florence/Venice via train.

Appreciate any advice or opinions if I have a good amount of days to see the highlights in each city.

Thanks,

8/6/2017 Sun DEPART FOR Italy
8/7/2017 Mon Arrive in Rome - AM
8/8/2017 Tue ROME
8/9/2017 Wed ROME
8/10/2017 Thu ROME
8/11/2017 Fri Travel to Florence
8/12/2017 Sat FLORENCE/PISA
8/13/2017 Sun FLORENCE
8/14/2017 Mon FLORENCE
8/15/2017 Tue Travel to Venice
8/16/2017 Wed VENICE
8/17/2017 Thu VENICE
8/18/2017 Fri Depart for US

It looks good to me, but it would partly depend on your interests and what you want to see and do in each city.

You don't say where you're coming from, but if it's North America, you might want to arrive in Venice and leave from Rome. Flights out of Venice tend to depart very early, because they all have a stopover somewhere. From Rome, there are many direct flights to North America, and they don't have to make any connections in Europe, so they can leave somewhat later. However, check flight schedules to your home airport, and see if the departure times are reasonable.