We no longer have a sofa that folds out into a bed – only an inflatable single mattress. If you want to sleep on the floor, you are still welcome. It might be more comfy to find an airbnb or hotel, though. I updated the public transport info:
I recommend the Navigo pass for a week (attention! information en français!). It is valid in all 5 zones in the Paris area, including the train to CDG airport. Versailles and Disneyland Paris are in zone 5. It really covers a big area. The chip card itself costs 5 €, you will need a passport photo. After you purchase the chip card you charge the card with the “forfait semaine” at the machine. The weekly pass costs 22.50 € and is valid from Monday to Sunday.
A single trip from Paris city center to CDG airport is 10 €, so the Navigo is really the cheapest option if you arrive and leave by plane all within one calendar week.
If you don’t want the navigo, you can get a booklet of 10 Metro tickets for 14,50 €. The transfer rules seem overly complicated, but generally you’ll be able to use them to get to the sights and back. There are tourist tickets, called Paris Visit, but they are all more expensive than the weekly Navigo pass. The regular day passes you can buy at the machine aren’t valid for the airport.
We live in Clignancourt now in the 18eme arrondissment. The closest metro stops are Jules Joffrin (line 12) and Simplon (line 4).
From Charles de Gaulle airport (CDG) you can take an RER B to Gare du Nord and change into the 4 there.
There’s a second airport, Paris Orly. Transavia serves this airport. There’s a driver-less shuttle train called Orlyval that’s fairly expensive but takes you to the RER station Antony within a few minutes. If you are lucky there are no kids you have to push out of the way to be able stand in the front and pretend you are the train driver. Antony station is south of Paris, but on the same RER B line. You can take the RER to Gare Du Nord and the 4 from there.
If you come by train and arrive at Gare du Nord it’s just a few stops with the Metro 4.
If you come by car: you are on your own. I know nothing about parking or driving in Paris, but I hear it’s a nightmare.