For in case you get only a 1 week stamp in your passport, can you apply in that case for a visa extension ? (when you make sure, it arrives in time in Vegreville).
But in fact that will be an evidence that you misled border officer in terms of your purpose of visit. For example, you told him your only coming for a wedding for a week but in fact you wanted (and knew it at the border crossing) that you are going to stay longer. CIC does not appreciate such a quick "change of mind" and probably would not extend your stay.