We stayed at Camping International in 2002 and we were able to buy train passes at the campsite. My recollection is that they had day and multiple day tickets available. It worked somewhere along the lines of you got the pass at the campsite and them paid for it and had it validated at the station.
Maison Lafitte is a leafy suburb and we felt perfectly safe walking back to the camp site late at night (we had a 21 month old with us). On our last night we had been at Disney and stayed until the fireworks so we were very late back.
We were there with Eurocamp and they claimed that the journey to Disney was 45 minutes by train but it was much longer than that.

thanks for that

I'll update the thread when i get back if they still do the tickets @ the site

Back from Paris 4th june
well the train station is used to us Brits and its easy to get tickets

best to get mobilis zones 1-4 for Paris and zones 1-5 for Disney
felt safe using trains just the same as using the tube back home (but then there was armed soldiers at every tourists spot,, )cost for mobilis zone 1-5 adult 12.10 eur child 6.40 and can be bought in advance the station is just a short 10 min walk from camping international campsite ( so no taxi needed) The surrounded area around was nice houses like the ones off aristocats