8 days in Switzerland

All of this is weather dependent. Interlaken is a transportation hub for things up the valley, not worth seeing itself. Wengen and Mürren are on opposite sides of the same valley, pick one.

How about Lucerne?

Is Switzerland your only destination? Will you be coming in jet lagged?
Eight days is not a lot of time. I'd suggest 4-5 nights in the BO ( Wengen or Murren) and two nights in Lucerne. I couldn't tell how many nights you are actually in the Airbnb.
Zermatt is too much and adds too much transit time.
Enjoy this beautiful country.
Have a great trip!

Lauterbrunnen - Zermatt is about half an hour longer than Lauterbrunnen - Luzern, so it is definitely not too far to go!

Would you rather do more mountains/hiking right from your doorstep (Zermatt) or be in a city and travel to any local mountains (Luzern)? Where is your next destination and it is easy enough to reach it from Zermatt?

Wengen and Mürren are on opposite sides of the same valley, pick one.

This makes sense if you are talking about where to stay, but you have said you are staying in Lauterbrunnen, in which case most definitely explore both Wengen and Mürren! In August there are more than enough hiking opportunities in the immediate area, you will not get bored there even if you decide to make it your only destination and not share your time with Luzern or Zermatt.

Thanks! Yes we wish we could stay longer but schedules only allow us for this amount of time. We had considered the 12 day RS tour but just could not make the dates work and then it sold out:) Once kids are off to college, we will do these tours:)

I guess I am torn on if we should stay in Lauterbrunnen the whole time or perhaps do 5 days in that area and then 2 days in Lucerne, perhaps Mt. Titlus/Mt. Pilatus/Mt. Rigi. Thoughts?

Thanks for everyone's input. We are getting snow in NC which is a rarity but a great day for planning the Summer.

I agree Zermatt is too much. You can see it on your next trip. The mountains will consume your time (weather permitting) that you could get enough of Interlaken and Lucerne while traveling through those cities. Harder Klum and Chapel Bridge were my highlights of those two cities. Consider Lake Brienz over Lake Thun for a lake experience. Titlus and Pilatus are possible with a longer scenic train ride. Murren and Birg has amazing views but I am 2 for 2 on bad experiences at the Schilthorn, crowded and crabby people. I enjoyed the First cliff walk more than the Birg Thrill Cliff Walk.