Hi Isay, and welcome to MySwissAlps!
>> We would like to do the Bernina Express route then go and explore Lauterbrunnen and it's sorroundings.
The Bernina Express route is a long way from Lauterbrunnen. Are you coming to Switzerland from Italy?
For a map of the panoramic routes, please see the map at the link below. The Wilhelm Tell Express is now called the Gotthard Panorama Express:
www.sbb.ch/content/dam /sbb/en/pdf/en_bahnhof -services/en_am-bahnhof/en_unsere-bahnhoefe/panoramic-routes.pdf
>> Lauterbrunnen ... I believe we can go to Jungfrau from there.
Yes. For information about going up to the Jungfraujoch, see this page:
>> Where can the four day Swiss pass take us?
You can download a map from the link below, showing what is covered by the Swiss Travel Pass
As explained in the legend on the map, red lines are trains, yellow lines are buses, black lines are cable cars, white lines are boats. Solid lines are free, dotted lines are discounted. Discounts are mostly 50%, but only 25% for transport where you see the number "1" inside circle near the dotted line. There are a few grey lines on the map as well, which indicate transport that is not covered by the Swiss Travel Pass.
You can use the Swiss Timetable to plan your trips and find out about travel times.