Getting to the Airport from a DLP hotel is easy - the buses stop outside every hotel, just ask the concierge for a timetable. Fare is 14 Euros per adult I think (from memory).
The only two warnings I would give are :
a) if you are leaving on a Sunday afternoon, watch out because everyone else is too! The buses will be very crowded if not full and you may have to wait for the next one, so build that in to your timings. Especially if staying at the Newport Bay Club (last of the pickup points).
b) Make sure you check the front of the bus as they go to CDG and Orly airports and the driver assumes you've picked the right one!
As for getting to DLP from the Chunnel, do you mean you're coming across by train or by car?
If by train, I assume you'll be arriving in Paris (i.e. not on the direct to DLP train). If so, you'll need to take the RER train line A to Marne la Vallée station at the end of the line.