brandont, if you want them to be able to submit assignments and take quizzes, then you need to add them as students. In addition, if you add them to the course as teachers then you would constantly have to worry about one of them "accidentally" messing something up. We had a large course where the teachers were added as teachers and one Sunday evening an Instructor thought she'd "clean it up" a bit for us and deleted EVERYTHING out of the course. Yeah... after that it is student (or other limited) access only for pretty much anything that has to do with training or involves important/sensitive information.
Side note, I will say that while our faculty are in as students in our training course(s), they each have their own Sandbox course where they are the Instructor and can play around and try out the Canvas features, build a course, etc.
