The district for disney is number 77 - seine et marne. There looks like there is a church called St Genevieve in Magny-le-hongre which looks near to the hotels and has Mass at 18.30 on Sunday evening. I don't know how easy this would be to get to.
You're going to worship someone else than the MOUSE while there?
Just kidding. Magny-le-Hongré isn't that far from DLP, I think there's even a bus going there (not a Disney-bus, a regular one).
For those who want to know where it is, more or less: you take the road the shuttle busses to the hotels take from the train station, at the lights you make a left turn, pass by Santa Fe until the roundabout at the Neighbourhood hotels. Instead of going to those hotels, you turn left, and at the lights you turn right, keep on following the road until you're there.