It's about 90 km from Montreal to the park, using dedicated trails mostly on a disused tramway line.
Here's some pictures of that route:
There is also another itinerary following the Chambly canal then another disused rail line from St-Jean-Sur-Richelieu but I never tried it yet.
And here are the two other pictures of the camp sites I got in the park for previous weeks. We can clearly see the difference in the foliage!
Then, from the park, I cycle a bit more (40 km) on another rail trail to my destination. And back! It's a really nice place for rail trails. I'm glad summer is back!