Register the birth with the local 'Registro Publico' and get the proper paperwork. Your child will be Mexican, by birth, and entitled to a Mexican Passport.
Register the birth with the Canadian Embassy or nearest Canadian Consulate, and get the proper paperwork. Your child will be Canadian by descent, and entitled to a Canadian Passport.
Get both passports. That's dual citizenship. In Mexico, the child is Mexican. In Canada, the child is Canadian. The appropriate passport is used when entering each country.
As the wife of a Mexican and the mother of a Mexican, you will find it very easy to get naturalized, yourself, after a couple of years in Mexico with a visa, and also enjoy dual citizenship's benefits; the main one being freedom to work and freedom from having to deal with INM any more.