I'm not intending to make my self unpopular or sound disagreeable, but a US citzen can enter Canada without a passport.  Look at entry requirements at teh Canada Border Services Agency site.

"Non-Canadians - Requirements to Enter Canada.
When you enter Canada, a CBSA officer may ask to see your passport and a valid visa, if one is necessary. If you are a citizen of the United States, you do not need a passport to enter Canada. However, you should carry proof of your citizenship, such as a birth certificate, certificate of citizenship or naturalization, as well as photo identification. If you are a permanent resident of Canada or the U.S, you should bring your Permanent Resident Card with you."

You don't need a passport to get an RABC either.

To return to US by land or sea, you will need a passport (or one of those passport cards) if you are 16v or older.  Under 16, a birth certifcate (original or notarized copy) is acceptable.  I think you may need signed consent forms if both natural parents are not with a child.