I agree with the firts statement,i find that all age groups like songs, i think this is because they like rhythm,move and enjoying with this.
In the second statement, I agree because the ss can remember the last class topic, we can use different activities, using tha last vocabulary, they can remember, play and enjoying the activity.
In the third statement I think is important preparing extra material, because in all groups we have ss who finish early and they don`t have nothing to do.