Hi Sunnybunch -
Welcome to My Swiss Alps.
Your friend is correct about Interlaken, in that it is not a scenic destination, and is fairly commercial. However, it is the best transportation hub if you wish to visit other places - such as Brienz, or Bern, because it is on the main rail line. But, for what you describe near the Jungfrau, I'd avoid having an automobile. And. I'd stay in Wengen or Lauterbrunnen. Wilderswil is less commercial than Interlaken, but the villages further in the valley have a totally different atmosphere, and would improve your overall experience. Each has pluses and minuses -
check this link and the sub-links:
And, for a really useful bit of light reading:
Without knowing all your plans, (such as where you go after Interlaken) I can't be definite about using a car, but, certainly, around the Jungfrau, it will spend most of the time being parked. And, rail travel in Switzerland is a great tourist event in its own right. So, we tend to recommend rail travel. On the other hand, rail travel for four can be more expensive than car rental, unless you try to drive, park, and stay over in major cities. For example, if you park at the main train station parking lot ... a very good location for the center of Luzern...it costs roughly 5o CHF per 24 hours, and hotels near the heart of town, except the super luxury ones along the lake, usually don't have parking. It i easier to haul luggage with a car. Howeve, a rental car that holds four people and claims room for a bunch of suitcases won't have a very large trunk. You may find that you need a more expensive rental to handle your whole entourage.
Here is one thing that you may not have considered. Early-mid May is still pretty much the disagreeable end of Winter at the higher altitudes. Lauterbrunnen at about 700 meters is probably pretty well clear snow on the trails, but by the time you get up to 2000 meters, there a lot of late Winter snow residue.
<<"if the boys and my husband want to walk to Trummelbach Falls one morning. ">>
The wonderful trail from Männlichn to Kleine Scheidegg at around 2000 merers won't open till early to mid-June.
Cableways and the Shynige Platte line don't start running until May 25th, as i recall:
The cograil to the Jungraujoch runs all year.
Mid -May near the Jungfrau is definitely low season. Many but not all hotels and restaurants in the villages are closed for between seasons break. Bad snow, no skiers, no hikers, no customers.
You can do some of the major things, and two or three days will be a positive experience, but, as you read about attractions, check out whether they will be open when you are there.
Tat will get you started. Let us know your thoughts.