Hi, my family of five (includes kids 11, 12, 14) will be disembarking in Rome (scheduled arrival 5am). We'll be staying near Castel Sant Angelo, but check-in is in the afternoon, so we're not in too much of a rush. Should we pre-purchase train tickets? Or is there a lot of availability on the spot? What is a reasonable time to get the train if we're walking off with our luggage? Is it fair to assume that we should get off at Termini and then take a taxi? Or is a walk from S. Pietro manageable? Thanks in advance.