Bernese Oberland Pass

Interlaken and Wengen are close by. Unless you have a specific reason to stay in Interlaken on day 1, I would recommend simply staying all 4 nights in Wengen.

How are your arriving and exiting Switzerland? That would help determine the best rail pass for your itinerary.

We are arriving and departing by car. We will be parking at the car park in Lauterbrunnen. Never thought of that, guess we figured it would be too much travel back to Interlaken from Wengen

Ah, nice. It looks like the B.O. pass jumps from 4- to 6-days at 240 SF and 300 SF, repsectively. It may be better to just pay for the last day's tickets individually rather than buy two 6-day passes.

Alternatively, you could look at getting two Half-Fare Cards. They are valid 30 days and discount all transportation tickets by 50%, including the pricey Jungfraujoch excursion. A HFC costs 120 SF each, so it pays for itself if the full-fare value of your planned tickets is more than 240 SF.

Usually, the HFC is the cheaper option but you would have to do the math on your best guess itinerary to know.

great information, thank you

Based on 4 trips to the Lauterbrunnen Valley, I would advise a 4-day pass and pay for your last train out on Day 5. Stay all nights in Wengen. You can take the train back to Interlaken (20-minute ride) for anything you want to do there. The BO Regional Pass will allow you to ride without additional fare on any lift or train. You pay a supplement for the Jungfraujoch and Schilthorn. Once you get there you will find how great it is to have the freedom to jump on a lift or train and joyride, if nothing else.

Once you get there you will find how great it is to have the freedom
to jump on a lift or train and joyride, if nothing else.

Yes, I opt for a pass rather than a HFC for this same reason, even if it costs a little more.