There are 4 RV parks just off of Autoroute 15 which is I-87 in US. The exit is Montee Monette. They are about 20 miles from center of Montreal. We generally use the Metro to go into the city as parking is difficult. There is Camping St Andre where we stay (no pets), Camping Amerique right across the road, KOA right on Montee Monette, Bonaire and Cle de Champs nearby. 
A couple of these are Passport America Parks.
There is also Camping Alouette on autoroute 20 which is a bit more expensive and not as convenient to get into the city. 
If you want any more info let me know. 
This is a great area for bicycling if you enjoy that. Many dedicated bike paths as well as Costco just up the road.
Sidney