13 Days Tentative Plan, Open for Suggestions:)

Sounds like an awesome trip! Keep your day plans loose and select which thing you'll do based on weather and webcams that morning (MeteoSwiss, MeteoBlue & Bergfex). I'll list day activities based on weather....

BEST WEATHER DAYS (in order of priority to pick for nicest days)
**Murren > Schilthorn > Birg > hike roundtrip Birg/Grauseeli/Birg (bring hiking poles) > Murren (you haven't said if you're a good hiker, but if you are you can continue from Grauseeli to the Wasenegg Ridge and down to Murren but you need to be okay with your knees experience lots of downhill - it's an amazing hike if so)

**Murren > Allmendhubel > Northface trail counterclockwise (allow more than 2.5 hours and stop at Suppenalp for lunch (open Wed-Sun)) > Gimmelwald > Murren

**Murren > Grutschalp > Lauterbrunnen > Wilderswil > Schynige Platte > Oberberghorn trail (allow more than 1.5 hours) > Wilderswil > Lauterbrunnen > Grutschalp > Murren

**Murren > Grutschalp > Lauterbrunnen > Wengen > Mannlichen > walk to Kleine Scheidegg if trail has opened by then > do a fun/beautiful roundtrip ride on the Eiger Express since you have the pass (train from KS to Eigergletscher/Eiger Express RT/train Eigergletscher to KS) > Kleine Scheidegg > continue walking to Wengernalp > trail to Wengen (dinner) > Lauterbrunnen > up to Murren via Grutschalp or Stechelberg depending on time of evening

**Murren > Grutschalp > Lauterbrunnen > Interlaken Ost > Brienz > Brienzer Rothorn (do this before boat & make sure to get seat reservations for your time or you won't get on) > Brienz > boat ride (possibly do Giessbach Falls if you want, but skip Iseltwald, it's become a Netflix show tourist trap) -- you won't have time for Ballenberg on this day, just do the boat ride leisurely > Interlaken Ost > Lauterbrunnen > Grutschalp > Murren

**Murren > Grutschalp > Lauterbrunnen > Zweilutchinen > Grindelwald > Grindewald First > Bachalpsee > First > Grindelwald > if you have time maybe do Pfingstegg but don't prioritize > Zweilutchinen > Lauterbrunnen > return to Murren via Grutschalp or Stechelberg depending on time

NOT SO GREAT WEATHER DAY
*Murren > Grutschalp > Lauterbrunnen > Interlaken Ost > Brienz > bus to Ballenberg > Brienz > Interlaken Ost (Harder Kulm if cloud cover isn't too much and you want to mess with it, it's very crowded and inferior to views you'll see elsewhere) > Lauterbrunnen > walk the Lauterbrunnen Valley (waterfalls) > Stechelberg > Gimmelwald > Murren

In terms of doing Oeschinensee on your arrival day, in order to make this a reasonable choice you need to leave Chamonix early in the morning to allow yourself around 6-7 hours for the Kandersteg > bus or walk to cable car > ride cable car > walk down to lake > hike > back up to cable car > bus or walk to train station (20 min) > Kandersteg -- it's a lot of logistics to line up and you only want to mess with it if it's a very nice day, because if it's cloudy the lake won't look like all the instagram photos you've seen of it. We stayed up there on the lake for a week a couple summers ago and only had 1 or 2 days where the water looked like what you see in photos and the sun sets early there because of the steep cliffs so you want to be hiking earlier in the day.

Have a great trip!!

Hi wanderweg,

Thanks so much for your detailed feedback and provide alternatives for bad weather day. I have been hesitating packing poncho for August's trip but it looked like I have to.

We will only take carry on, no check in so hiking pole is not feasible. I checked with Adventure Sports, they have hiking pole for rent. I will bring knee brace and hopefullly it will help. I wouldn't consider myself a good hiker but leisure hiker. I have knee issue when going downhill so I need to be selective on which hiking trail to take.

Yea, for Iseltwald, it seems a nice place but I'm not going for korean drama spot for selfie:)

For Harder Kulm, is it better to go during the day or during sunset? I read that sunset is great there.

For Oeschinensee, I'm afraid if I don't go, I might regret later.....Logistically, as Lola has suggested, it seems to make more sense if I visit there on the way from Chamonix to Murren instead of taking a seperate trip from Murren to visit there on another day. I do hope for great weather to see the famous blue water.

Thanks again!

Sorry I don't know what Adventure Sports is. Do you mean Intersport? I think you can rent them down in Lauterbrunnen but not sure about Murren. If you have knee issues then definitely don't do the Grauseeli/Wasenegg/Murren addition I spoke of. And you may find some trouble on the Oeschinensee hike as well, as there are some steep portions to go downhill. The Komoot app for figuring out hiking elevations will be helpful. There is an initial small section of the hike from Birg to Grauseeli that is loose scree and a bit steep, so definitely do not attempt without hiking poles and be prepared to take that portion really really slowly.

Iseltwald was a nice place until the show. Now it's hoards of people standing in line for selfies, which is sad to see, as we used to enjoy it so much.

Harder Kulm is one of those things that's easy to get to from Interlaken for tourists who are in and out in a day, which means that it's extremely packed at all times of day/night. It's a tiny funicular so the wait to get down off the mountain can sometimes be hundreds and hundreds of people long. Sure, the sunset is nice up there, but personally I hate overcrowded Disney World line vibes. Sunsets are beautiful in many less crowded spots. But if you don't mind the chaos, go for it!

Sorry, I got the name mixed up, I meant Intersport. Yea, I have checked with Murren location on the rental.

Looked like I will have to skip the hike from Birg to Grauseeli.

I will save Harder Kulm as a backup. I sure don't enjoy disneyland in the Swiss Alps:)

I was at harder kulm last month and had no lines going up or down. From the time on my pictures, I was there around 10 am on a Thursday. I wouldn’t make a special trip for it, but if you’re at the Interlaken Ost train station, it’s a quick walk to see if it’s busy. I went up before my boat ride on Lake Brienz.

I would guess June early in the morning would be fine at Harder Kulm but when I went there in August in the late afternoon it was nuts. The line was hundreds of people long to get down.

Thank you for your feedback, Carrie.