Your timing is perfect then!
Regarding a train pass and given your travel plans a Half Fare Card will likely be your best bet. You can spend hours "doing the maths" -- planning out everywhere you would like to go, using www.sbb.ch to find prices, then going to www.swisstravelsystem.com and reviewing all the various passes to figure out which is most economical. Every time I do that with a travel pattern such as yours I've found that a Half Fare Card comes out on top. So save yourself the aggravation. You can buy one (each of you will need one) at the train station at Zurich or Geneva airport (or at other main rail stations). This gets you 50% off of train, bus, boat, lifts, gondolas, etc., including the pricey trip up to Jungfraujoch.
Are you planning to rent a chalet or are you doing multiple hotel rooms? I recommend the former as it would allow you to maximize your social time together. We have rented through www.chalet-service.com 15 times and have always been very happy. Can't recommend them highly enough.
My husband and I have been to the area 15 times in the past 16 years. I have a lengthy document that includes transport tips, lodging and restaurant recos, hikes, and things to do and see in the region. If you would like a copy send me a private message with your email address; it's too long to post up on the public forum (35 + pages)