I think it's quite good for kids to have some idea about piano learning before they have private lesson. My boy has attended the lesson before. It's a 親子班。
My boy did attend the MusikHarmony classes. It's more interesting for him than the Musik Piano lessons. He could play with different musical instruments and the teacher was very good. He was not quite ready for the formal piano learning (esp.樂理) at his age of app.3.5 yrs. old. He only completed Musik Piano 1