We have had a slight change in our plans for our trip to Italy in May. We are arriving at FCO at 06:25 on Sunday, May 4th. But, we now need to get to Roma Termini hop on a train to Venice to catch up with another couple in Venice later that day. We do realize that it will be a long travel day with adding on a 3h45m train ride, but we will deal with it. But, I have two questions.
1. It seems like the Leonardo Express may be the fastest & least expensive option for four of us to get to Termini. But, I am concerned how crowded the train may be and even if we could get onboard. Any advice or experience with this?
2. All of us will be travelling with carry-on luggage only, so we will be getting through FCO as quickly as possible. But, we are not sure exactly which train to Venice we will be able to make departing from Termini. Does it make sense to purchase the tickets in advance or wait until we get to Roma Termini? If I buy in advance and we miss that train, how difficult is it to have them re-issued for a later train?