I'm going in Sept - have you been before? Beautiful site with lots to do. Never been inJuly so can't tell you about trips to Disney, sorry.
You could do it by train, from Soissons, but it would be very long winded and you would need a car to get to the station.Buses are few and far between to the station from the site. You would have to go into Paris Nord and change. I found this useful and it wa sposted by another answerbank member for me a few weeks back - it's in English which helps
http://www.voyages-sncf.com/dynamic/_SvHomePag e?_CMD=cmdHomepageUK
Looks like the whole journey will take 2.5 hours :(
hth
ojx