Late afternoon arrival in Lauterbrunnen

The sun sets pretty late at that time of year, so you'll have several hours of light. I wouldn't expect it to become completely dark until after 10.

You could hike (walk on a level paved path) up the valley all the way to the Trummelbach Falls. I think its about 45 minutes. Entrance to the falls (they're inside the mountain) might be close by that time, but there's a nice park in front of it.

Just get out and walk...the whole area is full of paths and trails. The road from Lauterbrunnen to Stechelberg becomes less and less traveled the farther you go toward Stechelberg. It's not difficult to find an interesting place to walk!

Being a bit of a planning nerd, I always include the sunrise/sunset times in my planning spreadsheet. You can find the info here at TimeandDate.com for Geneva in June. As Tom said, you'll have daylight quite late. I think you even have time to take the lift to Grutschalp and walk to Muerren, then return via the lift down to Stechelberg and the Post Bus back to Lauterbrunnen. The lift back to the valley runs as late as 21:55 according to the SBB site. The walk along the cliff from Grutschalp to Muerren is a good stretch of the legs.

Actually the Schilthornbahn gondola from Murren to Stechelberg departs Murren as late as 23:45 and arrives into Stechelberg at 23:55.

The route Murren BLM -> Grutschalp -> Lauterbrunnen departs Murren as late as 19:58 and arrives Lauterbrunnen 20:17

Thank you all for the input. It's what I needed in order to plan the rest of that day. My wife and I really wanted to get in a good hike to counteract all that time sitting on a train. And it sounds like we'll have good enough daylight to get in a good hike.