I wanted to know whether I need to purchase a separate Navigo Découverte for a kid under 2 years of age. For this kid, is a Paris Visite required (in case I'm forced to buy it at CDG as has been experienced by some tourists). Thanks.
Children under 4 years of age ride for free on Paris city transport (Metro, Bus, RER, Transilien) as long as they don't take up a seat (i.e. sit on your lap). No transport fare is required for them. Between ages of 4-9, a transit fare is required, usually at a discounted price (except Navigo, which has no discounts for children).