The word used was 'teaching', so is asking for the best starting point. The piece of music likely to be attempted at this point is irrelevant, as the OP specifically mentions a beginner, not an experienced player.

When you teach a beginner, you should ALWAYS encourage 'best practice', as lazy techniques will not breed good playing.

It's far harder to shake off poor technique later than it is to learn good technique from the outset.

I'm all for 'instant success', which is why I start off with D and A7 - lots of songs use just two chords (some you can even get away with only one!), but stressing the importance of proper fingering and a good strumming technique are paramount, even on the first lesson.

I've always found adults harder to teach than children, because they always want to put their own 'spin' on things rather than accepting that 'teacher knows best'...!