I may be COMPLETELY wrong, but I understood that the TGV and RER went in and out of the one station at DLP. Somebody please correct me if I'm wrong!
If you would like to know how to get to the TGV station at the airport, I saved this nugget of information!
"You have to take the airport shuttle bus (free) to terminal 2 (bus number 5)which then runs in a loop and get off at the station. there is a display board on the bus in english and french telling you which stop. (We landed at terminal 3 so to find the bus stop we had to exit the arrivals building and turn right following the pink number 5 sign and walk for about 300 yards so a trolley for your luggage would be a good idea).
As you exit the bus you then go down 3 levels to the TGV station (all well signposted) and either go to the ticket office on your right or to the automatic machines which are also in English and take credit/debit cards, to buy your ticket.
The information board tells you which platform to go to and you have to punch your ticket in the orange machines before you board the train.
The signs on the platform tell you the number of the train and what time it is due. The train arrives bang on time and departs bang on time.
It takes 9 minutes and you get off at the first stop, Marne la Vallee Chessy. When you exit the station the bus terminus is right in front of you. The park hotels have free shuttle buses that take you to the hotels every few minutes."