I have used both the TGV and the VEA shuttle buses to go from CDG to Disneyland and, personally, I think the shuttle buses are the cheaper and more convenient option, especially if you have small children in tow.
For instance, if you arrive on an Aer Lingus flight at Terminal 1, taking the TGV from CDG to Disneyland involves:
1. Stepping a shuttle bus at Terminal 1 to Terminal 2. Due to road works this journey could take 30mins.
2. Making your way to the the TGV station at Terminal 2, which involves going down 5 floors, and lifts don't always operate!
3. Waiting for a TGV - TGV go every two hours or so *
4. Getting the TGV to Disney - this journey takes 15mins.
5. Climbing up one flight of stairs at Disney and walking out to the bus stop.
6. Stepping on a shuttle bus to the hotel.
*
http://www.bonjourlafrance.net/fran...de_france_avignon_marseille_nice_toulouse.htm
In comparison, taking a VEA shuttle involves:
1. Stepping on a VEA shutltle bus at Terminal 1 to be dropped at the hotel door 45mins later. Due to road works this journey could take 60mins.
Buses leave every 30mins.