First you are on the Province of Québec general forum. It would be advisable to post your request on the Montreal page.
But since I am a DE for Mtl I will give you some informations right here.
For shopping, downtown visit Simon, real European flair at very reasonable prices.
Saint-Denis Street from Sherbrooke to Mont-Royal. Also the street is very large in that area so you might have to walk on one side and then return on the other. Rue Laurier from Saint-Laurent Boulevard to Côte Sainte-Catherine.
Picnic. Sainte-Hélène Island in Parc Jean-Drapeau.
Saint-Paul in Old Mtl and Sainte-Catherine in the Village are pedestrian only in summer.
Museum of Fine arts is free for the permanent collection and it has just expanded so now more Canadian art can be shown but also much more of their huge design and applied arts collection is also featured