Mirren is absolutely one of our favorite places in the world. If you have the option, try going in shoulder season: late August or early September. The Lauterbrunnen Valley has absolutely been loved to death, and is swamped in June / July.
We love to stay at altitude, and come down to the Valley during the day. It's more expensive, but you go against the day-tourist flow, so a lot of frustration is avoided.
Switzerland is always expensive, particularly relative to other European destinations. One thing we do, as a group, is to rent a flat rather than 2 hotels rooms. You can save a lot on the room rate, particularly outside of ski season. It will also encourage you to make your own breakfasts, at least.
At altitude, we have found buying meat to cook ourselves wasn't much of a savings over going out.
If serious hiking is out, but hiking and vistas might be desired, take a look at the Mannlichen route to Kleine Scheidig. Gondola up from Wengen, and it's pretty flat until a couple brief slopes down at the end.
More adventurous, that we loved, is hiking up to or down the Schilthorn from Piz Gloria. The first gondola of the day is discounted.
Agree Jungfraujoch is shockingly priced. Lots of tourist things, and snow in summer, if that is novel for you. Of course, plenty of that in Alaska, so that would be an easy skip,
Lots more places to go. And French/Italian/Austrian Alps are lovely, too. More details could help get more specific advice.