But qualifications in teaching music are precisely what they say on the tin. They are qualifications in teaching music! Of course that's different to teaching English or Maths 
I'm trying to step back from this thread, but the arrogance of the OP keeps drawing me back in.
You seem to believe that qualified music teachers teach by the book, focus on notation and the western classical tradition. Have you observed a qualified music teacher take a class? The strategies you talk about are commonplace amongst qualified music teachers - precisely because we have spent time studying, learning, researching, being trained, observing and practising techniques for engaging children in music. I'm sure you are talented and capable - but the way you post implies that you scorn the very idea of teaching qualifications for music teachers. The PGCE in Music is a very, very different course to a PGCE in English, just as it is different for PE and for Art, obviously - it is delivered by specialists.
People on the thread are also confusing peri teachers (excellent musicians who teach one-on-one or small groups on specific instruments) who have music degrees and usually a professional performing career alongside, with postgraduate qualified music teachers who dleiver class music lessons in the manner described by the OP.
The issue is not that we should have more unqualified people teaching music in our classrooms - it is funding, pure and simple. There simply isn't the funding for primary schools to have music specialists unless they choose to employ one (academies and free schools). Therefore they scrabble about doing whatever they can to provide a quality musical experience for children, which is usually the class teacher delivering music often poorly, or sometimes as in the OP situation, parents volunteer to help. Both situations are supplemented by visiting peri tutors.
What the OP is doing is admirable, but she is displaying a tremendous arrogance and lack of insight into what music teaching involves - and seems to think she is reinventing the wheel. Be humble and learn - you owe it to the children you will be teaching to become as well qualified as you can. The school can afford to employ you - they should support you in becoming properly qualified.
A qualification is much more than a piece of paper so please stop denigrating the thousands of dedicated professionals who teach music up and down the country.