9-day Switzerland itinerary in May – thoughts?

Thanks to the great resources and comments from this forum, we are heading to Swiss in one week’s time and have planned our 9-day Swiss itinerary as below. We are a group of 6 persons (3 couples) from Hong Kong and will travel to Swiss between 17-25 May 2018. Any comments or reminders about our plan are welcome. Thanks again.

(A) 17-20 May (Stay : Grindelwald)

17 May : Travel from Germany to Grindelwald by train (via Basel). We have bought train tickets from Germany to Basel. Starting from Basel, we will use the 8-day STP which bought on-line a few months ago.

18 May: Cable car from Lauterbrunnen to Grutschalp; Hiking (Grutschalp/Murren Gimmelwald) in the morning; Tour around Lauterbrunnen in the afternoon. (Our alternative for the hiking route is First/Bachalpsee but not sure if it will be open or not)

19 May: Jungfraujoch in the morning (depending on whether, may change to other date, buy tickets on the spot)

20 May: Interlaken/Harder Kulm (buy tickets on the spot)

(B) 21-22 May (Stay : Zermatt)

21 May: Travel from Grindelwald to Zermatt in the afternoon

22 May: Gornergrat (buy tickets on the spot); Hike from Rotenboden to Riffelsee/Riffelberg in the return trip (if weather is fine)

(C) 23-24 May (Stay: Zurich)

23 May: Take Glazier Express from Zermatt to Andermatt (Seats reserved), then take the train from Andermatt to Zurich

24 May: Luzern (boat trip and city tour)

(D) 25 May (Leave Swiss) : Zurich City visit (1-day ZVV pass for 3-zone) and free bikes ride; heading to Zurich Airport in the evening.