Posted: 30/03/2015 at 16:58
15West, are you flying into CDG? You almost certainly will want to just buy a single ticket from there into Paris on the RER (or a packet of 10 of them if there's at least 5 of you going both directions). Any kind of pass that includes zone 5 will likely be more expensive unless you plan to travel that far outside of Paris every day (zone 1 is Paris proper, with higher zones farther outside of the city. Both Charles de Gaulle airport and Disney are in Zone 5). Then you can figure out the best option for traveling within Paris. Most likely the best option is to buy books of 10 T+ tickets, which work anywhere in Paris for any combination of Metro/RER/Bus.
Details: a single trip between Paris and CDG costs 10 Euros, and a single trip betwen Paris and Disney costs 7.60 Euros. So a return trip to both is 35.20 Euros per person. Tickets for the Metro/RER/Bus within Paris are 1.80 each, or 14.10 for a book of 10. Compare that to an unlimited "Paris visite" pass, which is 50.05 for 3 days or 61.25 for 5 days for zones 1-5. Unless you're making a large number of trips, the Paris visite will probably be more expensive.
A much cheaper unlimited pass is the regular weekly pass, "Navigo semaine". However, the start day is not flexible -- it only goes Monday to Sunday -- so you will probably not get a full week out of it and that affects whether it's a good option. It's 35.40 Euros per week for zones 1-5, and I believe if you don't live in France you need to buy the "Navigo decouverte" card for 5 euros first. For just traveling in Paris (zones 1-2), it's 21.25 for the week.