You won't have to rebook:
"Members can change their Earnings Style at any time. The Earnings Style Option in place for a Member as of 23:59:59 U.S. Central Standard Time on the day of check-out for a given stay will be the Option that governs earnings for that stay. No changes can be made retroactively for past stays."
Therefore you could book a bunch of stays in advance (like you've already done), and change your earning choice for each stay as it happens.

As far as the offer: Looks it is good for all properties worldwide, even though it is being promoted by properties in Canada. Was there a code or a link associated with it?

Even though my main flying time was with United, I signed up for Aeroplan for specific offers when flying Air Canada within Canada. Only a few times. But I'm over 25k with Aeroplan mainly via HHonors double dip. Haven't flown AC in years, so I send some miles that way each year to keep them active. Aeroplan miles expire 7 years after earned, so I need to use them soon.