I am arriving next Saturday at Orly airport and will be staying at a hotel close to Gare de Lyon. Every day Sunday-Thursday I need to take the train to Disneyland for a conference, and Friday I am leaving through Charles de Gaulle airport. What is the best travel card for me to buy, and can all the different travel cards be purchased at Orly airport?
Navigo Découverte will cover you from Monday till Thursday between Gare de Lyon and Disney.
For Saturday/Sunday a 2-day 5-zone Paris Visite to cover you from Orly to hotel, hotel to Disney.
You can purchase Paris Visite at Orly (any ticket office). Navigo is apparently sold only from the Orlybus ticket office at Orly, but at any Metro/RER/Transilien ticket window inside Gare de Lyon train station.