I agree Männlichen to Kleine Scheidegg is a great walk. We did it both directions; as listed is best. If you have concerns about climbing up and down big hills or walking on tricky surfaces this a gorgeous, safe, not overly long path.
I'll expound a bit on the walk Jeff G. mentions above. The following might not be a fit for you in total, but parts could work, mainly the valley floor, or the little network of trails at the top of the Murren Funicular with all the plants an flowers labelled:
Another nice walk that's a bit longer we really enjoyed: start in Lauterbrunnen. Walk all the way up the valley floor to the the Gimmelwald/Murren cable car. Waterfalls and cheese vending machines along the way. Then take cable car to Murren. In Murren take the funicular up to the Allmendhubel flower park zone. Picnic at top of funicular. Walk the Mountain View trail back to Grutschalp, then cable car back down to Lauterbrunnen in the valley floor.
This walk has a few advantages. One is that being on the valley floor is pretty awesome - it's seriously beautiful ambling along past incredible lush pastures and geranium laden farm houses with massive cliff soaring all around you and waterfall all over the place. And then on the way back you get the huge views of all the famous peaks the entire way, and a real trail too - more of a trail and less of a little road like Mann-Kleine Scheidegg.
Though this route is a bit long, it uses cable cars to go up and down sparing lungs and knees a bit and maximizing time when you can be taking in views (not sweating like hog and looking at your feet). It's not pancake flat, but it's not a lot of elevation gain/loss for a walk in big mountains. Also, you can bail out here and there by public transit - you aren't pot committed to walking the entire way after you start. You can clip the length by starting with a bus trip part way up the valley, or walking down to the cog railway stop at Winteregg at the end.
You can easily start and finish in Murren if you are staying there, and you can travel either direction (although the valley looks most beautiful walking up it from Lauterbrunnen).
You can also skip the funicular part and walk the lower trail from Murren to Grutschalp via Winteregg. I've not walked this route but gazed upon it from above - it looked pleasant and seemed like it would have good views too, without the elevation loss and more rolling aspect of the higher Mountain View trail. (if someone know for sure please help out).
I'm pasting a link to a nice, clear illustrated image containing this route - picture worth a thousand etc: