first of all read the question really slowly to digest it.....
Discus....means give points for and against....how....means u should incorporate the techniques used by gwen harwood.....be valued through an examination of its structure, content and language...this practically sets the sturucture of ur answer....talk about structure of the poems (rhyming scheme, length of sentences etc), then content ( what its saying, how its saying that i.e. language techniques employed) finally the language, is it formal, informal, informative, emotive etc.
but one thing u have to do is link it back to the question as often as u can, don't ever write a single sentence that does nothing to sway the teacher and the students to share you idea and point of view in the speech.
also the purpose of ur speech here is to persuade...(very important for what language to use, and what points to include)...because ur persuading i would also use a lot of high modality words as well e.g. instead of "gwen harwood has used emotive language to convey the child's belief in his plan", use "gwen harwoods extensive usage of emotive language cleraly demonstrates the child's belief in his plan"..the second sentence basically tells u what to believe rather than merely provoking the thought.
anyways good luck.