That is a nice itinerary with lots of variety.
On Day 2, I assume you will leave your luggage at your Brienz hotel while you hike the Aare Gorge and visit the Giessbach falls. Maybe lunch at the charming hotel there?
On Day 4, you can make you travel from Grindelwald to Lauterbrunnen fun and interesting by taking the gondola and cablecar combo from Grindelwald Grund up to Maennlichen and then down by cablecar (Royal Ride on the roof of the cablecar available) to Wengen, then train down to Lauterbrunnen. If you have a Berner Oberland Pass (which I would recommend for your itinerary) all of those rides are fully covered.
Then head up to Muerren by cablecar and little train, leaving Gimmelwald for later (I will explain why). I do not know the basis for your lunch plan at Hotel Edelweiss, but I would recommend taking the Allmendhubel funicular up to the top and having lunch on the deck at the little mountain restaurant there (assuming it is a nice day).
https://schilthorn.ch/25/en/Panorama_Restaurant_Allmendhubel
Then take the North Face Trail back down to Muerren, make you way down to Gimmelwald to explore (actually not a lot to see there), and then take the cablecar down to Stechelberg from there. Why? That cablecar ride is pretty exciting, as you swing out over the 3000 feet drop down to the valley, descending close to the lifts eye to eye with the paragliders.
On Day 5, the Jungfraujoch train will not take you to Kandersteg. Do you mean to ride up to the Jungfraujoch and then head to Kandersteg?
The Berner Oberland Pass will cover your train travel to Kandersteg, and then to Brig the next day on your way to Zermatt. It will also cover the little gondola up to Oeschinensee.
https://www.berneseoberlandpass.ch/assets/Uploads/BLS-BO-Pass-M-23-WEB.pdf
We usually stayed up at Oeschinensee at the mountain inn there, but it is closed for overnight guests for various reasons. They are open for lunch. In Kandersteg itself we have stayed at Hotel
Adler which is nice, with a good restaurant;rant, and an easy walk from the train station.
It all sounds like good, and lots of fun. Enjoy!
