Dh and I just got back in May,2018...
We used Ezyshuttle, private car company. ( Picked us up at CDG from the flight over took us to our hotel in Paris) then again Picked us up on time at our Hotel in Paris, then took us to Newport Bay Hotel, at Disneyland Paris. Here's our reasoning and how we came to the decision.
1) We had thought about the going the route of the trains, but with the strike going on I did not want to take a chance on any issue's, Striking is a normal thing in Paris, and apparently it happens frequently. We did not use the metro or RER the whole time we were there, even the hotel suggested that we not use the trains, as we might get some where and not be able to get back. We talked to another American couple who went on a tour that left Paris using the trains, and then could not get back into Paris that night. So the choice was try to find a hotel in the village they were in, and hope the trains were running the next day.... or paying for to get them back, is what they ended up doing. The tour company tried to help, and arrange for them to share a ride with 2 other couples trying to get back into Paris, which one of the couple had a 6:00 am flight. Another thought, in France schedules really don't matter, they are not strictly adhered to, more like a suggestion. You might be able to get there on the train, but what time does the last train leave, and will you be able to get on it.
2) When staying at Disneyland, your park tickets are included, plus you get all the perks on staying on site. We were so glad we booked and stayed on site. Plus the last thing after walking all day, we wanted was to be packed on a train, then still once into Paris more walking back to your hotel at night...