Shaping of my itinerary!! Hopefully finalized!

Hi Fayewolf! I think you've made a pretty good itinerary. Try to keep it as flexible as possible, so that you can adapt to weather circumstandes just like you planned. If weather isn't splendid, you can also consider a boat ride over lake Thun or Brienz and combine this with a train ride along the shores back to Interlaken and Grindelwald. And yes, Bern is very nice to see and a great bad weather alternative. So are the Aare gorge, Trümmelbach falls and the Beatus caves, but they aren't open all year; since you're thinking of winter hiking I guess you'll be traveling either early this Spring, or next Fall/Winter?

If you're mainly looking for scenic beauty, I wouldn't go snowboarding if I were you. The Grindelwald area is beautiful and offers more than enough for a few days' stay. There are lots of further scenic viewing points including First, Männlichen and Pfingstegg, but again, it depends on the time of the year whether they're accessible.

I think you should consider a rail pass for your travel plans. The Swiss Card would be a perfect fit, granting free trips from Geneva Airport to Grindelwald, from Grindelwald to Zurich (Airport) and a 50% discount on trips you make during your stay.

In case you're looking for a hotel close to Zurich Airport: an overview can be found here. Hotels in Grindelwald and other towns can be found here.