Where should we change? We have plenty of time, but we need to know, where to change train an d where to get off. Les Halles is quite big, is there a long walk to the next train etc.
For Disneyland Paris to Eiffel Tower, with a wheelchair, I would suggest taking RER A to Charles de Gaulle Etoile / Arc de Triomphe, then exiting the station to ground level and taking bus #30 (which is wheelchair accessible) in direction Trocadero. Bus #30 circulates around the roundabout around the Arc de Triomphe. You will take Bus #30 to the last stop, getting off at Trocadero. The Trocadero has the best view of the Eiffel Tower in my opinion. If you wish to get closer to the Eiffel Tower afterwards, the journey will be a gentle downhill slope towards Champs de Mars / Eiffel Tower.