Mary & Tony's Place is lovely and so are they! Comfy couches, proper bedrooms, and kitchen with enough cooking stuff to cook some Blue Apron. Plenty of space - we were only 4 people but 6 would be easily accommodated.
The flat is super convenient to a shop where you can buy all the things you forgot, has the bus right on the corner and the metro a short walk away.
You are not IN downtown (good as far as I'm concerned!) but can get there easily.
Parking is ON STREET which did concern is on arrival but we didn't have any issue with safety of the car or finding a spot so it worked perfectly.
I would definitely stay again if we were back in Montreal.