We recommend you to bring a printout of your ticket when boarding the bus. If your e-ticket says that you need to bring a print-out to redeem the service, you MUST print it out. If a print-out is not required, you may show the e-ticket to the driver on your phone or another electronic device.
You may bring a car seat if necessary, although it is not a requirement. However, every person occupying a seat needs to have a ticket, even infants.
For most of the tours, children under 2 years who sit on your lap are not required to have a ticket, unless otherwise indicated on the tour page.