In a nutshell: This is a really modern archeological museum literally built on top of the older city infrastructure. It's the coolest. I loved actually going below ground level and getting an idea of Montreal used to look like. I would recommend this museum for all ages. Our group ranged from about 25-45 years old but it is also totally appropriate for school-aged kids as well.
I did the tour in French--and my spoken French is à peine acceptable on a good day. But there were enough context clues for me to follow along. And it was totally my fault as there are also tours in English if you check the times in advance (which I did not).
Before the tour, there is a short video of about 15-20 minutes on the history of Montreal and French Canada. It was super informative, so if you are a tourist or new to Montreal, this should be one of your first stops in the city. One other thing about the video: there are headsets included that provide translations of the video in about half a dozen languages (English was one of them).
The best part were these amazing diorama-type exhibits that are under plexiglass on the floor.