Hi Vikaro,
Since you are landing at CDG on Thursday and are staying for 3 nights, 4 days, I would suggest buying a two
Carte Paris Visite for 3 days and 6 zones (39,70€/person) + two single
Billets Ile-de-France tickets for
CDG-Paris (8,40€/person, which I'll explain in a moment). Your two-year-old child travels for free. The
Carte Paris Visite will cover you for unlimited Metro/RER/bus trips all around Paris and out to Paris Disneyland (Zone 5) for 3 out of your 4 days.
Since you're staying 4 days and the
Carte Paris Visite will only be valid for 3 days, you'll need a pair of one way
billets Ile-de-France for your wife and yourself to travel between
Paris and CDG Airport.
If you arrive late to Paris on your first day, I suggest you use the
billets Ile-de-France for travel into Paris, saving the full day of Carte Paris Visite for your last day. Or do the opposite if you arrive early on your first day. The
Carte Paris Visite starts counting days
upon first use, not when you buy it. Thus, you can buy it one day and start using it another without losing that day of included travel.
I hope this helps and have a great trip.
Best regards,
Ben