Jun 2, 2020 - 8:45 PM
in reply to Fun4
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and Welcome to My Swiss Alps!
Either region could easily fill a week or weeks with visiting and seeing your interests.
(By the way, thanks for providing the details in your post).
Wengen happens to be my favorite place to stay in the Jungfrau region, but there are plenty of good choices:
The four nice villages close to the Jungfrau are described in that link. Interlaken larger, and is a good transport hub, but it is not so charming or scenic as the four villages listed. Of the 4, Grindelwald is the most commercial and the most spread out. Lauterbrunnen is in the valley, with good connections and access to the waterfalls. Mürren and Wengen are up on the sides of the Lauterbrunnen Valley with great views.
The Jungfrau region is the better of the two for waterfalls.
I have attached some images from a trip in 2009, going up to Männlichen by cableway from Wengen, and walking to Kleine Scheidegg. That walk is spectacularly scenic and rather easy. Easy enough to have the nickname "The Grannies' Walk."
My then 8 year old granddaughter (and her mother) had a wonderful time on it, although I'm not sure about a 4 year old's stamina:
There is a nice playground at Männlichen. They have added to it since then.