Teaching music - especially guitar - to children is not as easy as one might think. You probably have some knowledge of mathematics, science, or history, and you may therefore be able to help your child with some of their homework. It is less likely,however, that you have much, if any, knowledge of teaching music. It is important to recognize that, even if you play an instrument, it doesen´t mean that you can teach it.
Teaching music is an art unto itself. The teacher needs to know the psychology of TUTORING, which is also fifferent from teaching a class full of students.
To be a music teacher, one must also be a very good performer. But being a good performer has little to do with the art of teaching - that is, tutoring. The music tutor must have a great knowledge of music and must be a great performer - but he or she must also be a master of the art of teaching.