The biosphere is a bit far from the city center of Montreal. It kind of reminds me journeying to the Hall of Science from Manhattan to Queens. We actually took the cab from Habitat 67 to the Biosphere- so we sort of cheated ;)
Anyways the biosphere is an AMAZING place to check out with kids. They have a lot of great exhibits and interactions! The prices are also pretty friendly and you can spend 1.5-2 hours there :)
The surrounding area is also very relaxing and nice! Check it out for sure!