Oh wow, thanks for the information I was just looking at the fine print and saw that not all promotions are combinable. I think we will look at your suggestion.
On our first cruise we let Oceania do all the flights, it was horrible. We still have a promo code for Air Canada so we can use that one. We briefly looked at the site of Air Canada and saw flights going through Montreal. We even might check-in a hotel there as we fly from Vancouver. With the promo code we can fly with a premium economy for less than the credit Oceania is giving us for doing the flights ourselves.