It would be great to hear from anyone going on that trip. It would be my first time in any of those places except Kolkata (I was there and in rural West Bengal back in 1988).
I'm interested in the scenery, wildlife and cultures of these places. In Kolkata I want to go to the house where my favourite poet - Rabindranath Tagore - was born. And I look forward to visiting Buddhist temples in various places. I'm particularly interested in visiting Taktshang (Tiger's Nest, Paro Valley).
I look forward to hearing from fellow travellers!