The hike up to the Chalet of Mount Royal is a sweaty workout but definitely manageable. The view is worth the sweat and tears! The photos do not do it justice since they lack the spatial element. There is so much open space and sky up at the Chalet.
My friend and I took the most direct path up Peele Street from McGill's campus. We walked on gravel and climbed up a lot of wooden steps. There was more climbing than walking so we didn't find wearing flats to be a large issue but the small pebbles do get annoying. 99% of the people wear sneakers/athletic shoes so I recommend bringing an extra pair of shoes if you can. At one point, there was a continuous staircase of 256 steps, which was the final set before arriving at a flat surface near the Chalet. It was an intense 15-minute climb in total!
From the Chalet, most people walk to the famous Cross. We headed to bus #11 instead, which took us down to Le Plateau neighborhood. It's a charming area with a lot of colorful houses, their winding staircases to the second level (French architecture?), murals, coffee shops, boutiques, and the famous Schwartz's Deli for smoked meat (pastrami).