You don't say whether you are driving or not so......
I've not stayed at the campanille but I have stayed in Bussy St Georges before, and it was really easy to get to DLRP. I wasn't driving so I took the RER everyday and they are really regular and the last one isn't until 1:30am so I never had to worry about getting back.
I've also stayed at Bussy with a car, a long time ago, and it should be easy to drive to Disney as it's pretty much a straight line (anyone help me out?)