First, stop now and save yourself.
ATH-YUL is Air Canada Rouge, which is THE WORST rated airline in the world, worse than Spirit and Ryanair.
http://www.airlinequality.com/Forum/air_canrge.htm
If you do decide to torture your family with Rouge, 60 minutes seems to be the minimum connect time, and 75 minutes is doable at YUL.
And yes, AC would rebook them.