Honestly, I just don't think there is much you can do with the time available and all you'll be thinking about is making sure you get to the airport in time to check luggage, go through CBP and security and hit the duty free! I'd just make my way to the airport and cool my heels a bit until luggage check in is available.
Depending on how much luggage you have and your ability/willingness to haul it around with you, a quick trip into Gastown is possible.