My son has been attending MS (Kln city) Saturday playgroup for two terms. The duration is 1.5 hr, half in Cantonese and half in English (Led by two different teachers in two different classrooms). The Cantonese session is mainly art & craft works and tea time, the English session is a kindermusik course, mainly music and follow teacher's movement.
I personally feel that my son doesn't learn much from the Cantonese session while the English session is okay. Teachers are not MS K teachers but they are in general kind and nice.