It would be during the week of 12th August 2019
I'd recommend RER A train from Disneyland to Charles de Gaulle - Etoile station, transfer to Metro line 6 direction Nation until Trocadero (3rd stop from CDG-Etoile) and exit there to get a spectacular view of the Eiffel Tower from Palais de Chaillot / Esplanade du Trocadero.
Ticket would be a basic RER ticket you can buy from the Marne la Vallee RER ticket office (the train station at Disneyland). Cost is 7.60€ / 3.80€ for yourself / child, one-way. The RER ticket is good for the transfer to Metro 6