Do any of the budget airlines fly from Cardiff to CDG? For a quick trip flying is the way to go unless you have the luxury of being close to the tunnel
Charles de Gaulle Airport, there is also Orly or Beauvais (don't go for that one - no train or shuttle).
Orly and Charles de Gaulle have the VEA shuttle - their version of the magical express shutle, takes 45-mins 1 hour to get to Disney and drops off at each othe disney hotels. I would prefer to travel on the TGV (high speed train) from the airport to disney - only takes 10mins and Disneyland and its hotels are right in front of you!!
Bristol airport is very close to Cardiff so if there are cheaper flights I woudl go from there!
The nearest and biggest airport is Charles de Gaulle. From here you can get high speed trains which take you to DLRP in 12 minutes, or take the VEA shuttle bus which takes about 50 minutes. If you get a package to include fiights and accommodation, it will often include VEA tickets as well.
If there are more than a couple of you, you may want to consider an airport transfer company. Lots of people on here do that and could recommend a good one to you.
If you look at the top of the board you will find a thread called Useful information - this has all the details on how to get there. It will give you all the links etc