Gatineau Park is fantastic,
http://www.canadascapital.gc.ca/bins...&lang=1&bhcp=1. I am a roadie, but I have been up there a few times on my old MTB with friends. It is a blast. It'll be a way for you to ride if coming from Orleans. But you can park a lot closer and ride up or in the park and pay.
Camp Fortune,
http://www.campfortune.com/en/ski/home.php, is supposedly even better though you have to pay to access.
I've heard there is good stuff in Kanata Lakes as well.