Canada has had the requirement for a passport, or Nexus card, for a number of years. Traveling with a Card only, allows you to pass through a border faster. But each member of the vehicle must also have such a Card. If you plan on flying back to USA you will require the Passport, not a card, as international flights require a passport. Something to think about if you become injured or need medical procedures. Remember that each Canadian hospital lists the costs for those without inclusion in the Canadian system. Those costs are expensive without having other travel insurance coverage.