It would not change the meaning, but it would change the tone or mood, and of course the rhythm, which is central to lyrics and music.

It changes not the absolute meaning but where you put the focus. In "Sweet child of mine" the focus is on the fact that the child is sweet and that sweetness is the sweetness of your child. If you say "My sweet child" the focus goes on the fact that the child is your child and only in second place that your child is sweet. So in the first case you aim at the sweetness while in the second sample you go with the emphasis that the child is your child.

i agree with you, it Is better the second option