Everything in Canada is more expensive than in the US so get as much here as you can including fuel. While I'm on the topic of fuel, keep an eye on your gage and know how far it is to the next fuel stop. At one of our planned stops, the only gas station in town had burned down a few weeks before and the next town was 50 miles. Depending on where you are in Canada, wildlife can be abundant so keep a sharp eye out on the edges of the road. After all, hitting a 1200 lb moose will ruin his and your day. Make sure everyone has their passport as you will need them for both trips across the border. Also have proof that any pets you bring are current on their shots. Make sure your credit card does the currency exchange rate for you and doesn't charge. Some charge, some don't. Same thing goes for ATM / Debit cards.
Lastly, if you plan on taking a firearm, check their laws carefully. You can get a temporary license to bring in most rifles or shotguns (but not all), however handguns are pretty much out of the question.
Hope that helps.
