I will be coming from Paris to Disneyland Paris with a wheelchair. Are there elevators in the train stations in Paris and also at the Disney train station? I see that there are escalators but will need an elevator.
The Paris to Disneyland train line, RER A, does have elevator access to train platforms at stations within Paris such as Chatelet les Halles. You will need assistance to board the RER train itself due to the platform gap, but the station/train conductor staff will assist you with that by deploying a temporary platform allowing roll-on/roll-off access. Please see the Paris transit wheelchair assistance page for more information about that.
It'll also be important that you check elevator status at the RER A station you wish to use prior to making your journey to ensure the elevators are in service at that moment. The link provided is for Chatelet les Halles station, showing platform & direction each elevator accesses. You'll want to see green check mark for "RER A EST" which is the RER A eastbound platform for trains going to Disneyland Paris. On your return journey, you'll want to check that Chatelet les Halles RER A OUEST (westbound) platform elevator is working to ensure you can ascend back to ground level.
At the Disneyland Paris station (Marne la Vallée) the train terminates at ground level so there are no elevators needed, just a platform for roll-on/off access. Again, the train conductor will assist with that.