I do not agree with the first statement. I find that all age groups like songs, since there are different songs for each age, only you have to know what songs to use according to age or ask the students the songs that are to their liking .
before starting the class I start with a warm-up and review some topics from the last class and finish with a game to ask questions of what was seen during the class.
I agree with this activity, I always prepare extra activities for students who finish before an exercise