Check into a budget hotel or hostel in the 10th/11th, Latin Quarter or near Gare du Nord for cheap transport links; options: Generator Paris, Ibis Budget La Villette or small private hotels.
Walk around Île de la Cité, view Notre-Dame exterior and visit Sainte-Chapelle for its stained glass (usually open 9:00am–7:00pm; check current times).
Climb to Sacré-Cœur for views and visit the artist squares around Place du Tertre; the basilica is free to enter though the dome/tower may charge a fee.
Attend Sunday Mass (typical main times around 9:30–11:30am) — options: Église Saint-Augustin or a parish near your hotel; check parish websites for exact times and languages.
Spend the afternoon exploring Disney Village (shops, entertainment and restaurants). Admission to the Village is free; opening hours vary by season but often 10:00am–late.
Attend Sunday Mass at the parish in Chessy (close to the parks) — typical Sunday morning times around 10:00–11:30am; check parish schedule for the exact time that day.
Choose Giverny to see Monet’s gardens (garden opens around 9:30am–6:00pm) or Fontainebleau for the château and forest; train + shuttle or direct train depending on choice.
Attend a Catholic Mass in the Latin Quarter; typical Sunday main Masses are around 10:30–11:30am and evening options around 6:00pm — check parish sites for exact times.
If you choose Chartres, attend Sunday Mass in Chartres Cathedral (typically morning times vary) or in Reims attend Mass in Reims Cathedral — combine worship with a full visit of the cathedral.