We are planning to go from venice to rome via Pisa in august. We are travelling with kids (2 adults and 2 kids).

Can you suggest how should we plan to make the most of our travel from venice to rome via pisa (florence).

Also do we have to buy the cheapest tickets in advance. If yes, how soon should we buy these tickets. What if we miss a train for whatever reason?

Please advise.

Pisa is an hour from Florence which is a bit over two hours from Venice. How many nights are you spending in Florence?

Between Venice/Florence, you would buy your tickets in advance on Trenitalia (120 days in advance is possible) to get the cheapest rates/discounted tickets for the fast trains. Depending on the ages of the kids, they might travel free.

Between Florence/Pisa, you don't buy these in advance as they are old,slow regional trains and there are no discounts, no reserved seating. Regional train tickets bought online have more restrictions than if you just buy them at the station.

If you will be staying in Florence, you would buy your Florence/Rome tickets in advance also.

From my reading of this, the OP hopes to travel from Venice to Rome all in one day, stopping in Pisa along the way. Is this correct?

If so, Pisa is not really along the way between Venice and Rome. You would have to change trains in Florence to reach Pisa, so I would expect it to take about 4 hours including connections to get from Venice to the tower in Pisa. Similarly, to travel from Pisa to Rome would take 3.5-4.5 hours, probably with at least one connection, depending on the time of day and the trains available.

A direct train from Venice to Rome takes 3.75 hours.

Rome from Venice is too long for a reasonable day trip. Add in Pisa and you have a trip to remember with total frustration of time spent and nothing seen. Throw in that you want to do it in August with two kids, and you have blistering hot misery

Just about the only way to do this is to take the train to Florence (2 hours), stow your luggage there (takes about 30 minutes), and then go to Pisa by train (a bit more than 1 hour). Unless you take a taxi, you will need to walk for about 25 minutes to the area of the tower. (If you get off at S. Rossore station in Pisa the walk is slightly shorter). Obviously you will need to go back to Florence to get your luggage -- so that is another 90 minutes + getting your luggage, and from Florence it is 90 minutes to Rome .

So once you are on the train in Venice, it will take you 4 hours to reach the tower. From the time you leave Pisa, it will take you about another 3.5 hours before you arrive in Rome. In August, you really need to be careful about staying cool in the midday sun. Were it me, and if the kids are not too little, I might time the trip to leave Venice later in the morning, so that I was visiting Pisa after 4pm. Buy food to eat on the train for both lunch and dinner, because if you take one of the last trains out of Florence for Rome, you won't get into Rome until 10pm or later. I would also budget for taxi rides in Pisa and your arrival in Rome.

Regarding advance purchase of tickets, it will save you a lot of money and really is a necessity in August to make sure you get seats. These trains can sell out. As for what happens if you miss a train, you could end up not making it to Pisa or not making it Rome and spending the night in Florence. Most of the time you can take a later train, but only if there are seats available.

Plan your trip so you don't miss any trains. Or plan to spend the night in either Pisa or Florence instead of trying to do this all in one day.

Actually, you can take a bus from the train station in Pisa to the Field of Miracles, where the leaning tower is located.

I understand the appeal of seeing the leaning tower, especially with children, but having just done this in May, as a side trip from Florence, I wouldn't encourage going out of your way to see it. This was the least favorite thing we did in Italy. The area outside of the Field of Miracles is filled with junky stands selling cheap tourist souvenirs. In the Field of Miracles, there will be hundreds (maybe thousands in August) of people, all trying to find just the right spot to snap photos of themselves "holding up the tower," which is more difficult than its would seem!

Perhaps there is some activity in Rome that your children would enjoy that wouldn't entail making the very long and arduous side trip to Pisa.