Switzerland in 7 days

Hey guys,

I am planning to visit switzerland for 7 days. My plan for the trip is (I have my first two days booking at Zurich done; but the rest is pretty open):

2 nights days in Zurich : Plan to make day trips to Lucerne.

/ St. Moritz.

2 days in Zermatt

2 nights at Interlaken (or) 1 night at interlaken and 1 night at Geneva.

Basically, I wanted advise on four things:

1. Which are the glaciers worth visiting on this plan? How to get there (I might be able to figure out how part.....but seriously which are big/beautiful ones)?
2. I have my 3rd night free; and was thinking if it was worth going to St. Moritz and take the glacier express to Zermatt. I plan to take the swiss pass and wonder whether it was worth paying the additional money?
3. My final two days is a split between being at interlaken or interlaken and Geneva. We are not interested in the cities; but have a flight to catch at noon that day from Geneva.

Thanks!