Is it best to go to jungfraujoch first and spend the whole morning there and then go down to lauderbrunner in the afternoon? Then take the train to grindelwald for dinner and go back to interlaken ost, which is our home base. As i've said, we are booked in Bellevue Hotel for 5 days. We are planning to buy the swiss pass in the airport as suggested by you guys (thanks!).