Confused by rail passes

Hi.

We're staying in Lauterbrunnen soon for nine nights. We are, however, getting very confused by what we need.

The party consists of two adults, one 16/17 year old, and two under 15s.

We want to do the Jungfraujoch, and possibly the Schilthorn, but other than that we have no concrete plans, happy to be guided about where else we should visit.

Do we need a Swiss Pass (which one?), or the Jungfrau Pass, or both?

Any advice much appreciated as I'm getting more confused each time I look!

Thanks in advance.

Oh, and does it make a difference whether we purchase in advance, or buy in resort?

Hi potter,

Can you tell me when exactly you'll be traveling? Where will you be coming from and how do you travel to Lauterbrunnen? Where do you travel after your stay?

Hi

We're arriving mid-August, travelling by car from the UK.

I think we will be using the car some of the time. Many thanks for your help.