You can make better use of your time by traveling from Interlaken 20 minutes into the valley at Lauterbrunnen.
Do you have 3 nights so two full days? From Lauterbrunnen, you can spend one day going up on the Mürren side of the valley and one on the Wengen side. Do you like to hike?
My two perfect days there would be to spend 1/2 of one day hiking between Grutschalp (just above Lauterbrunnen) to Mürren. You can then decide, weather depending, to go up the Schilthorn in the gondola or walk down to Gimmelwlad then take a gondola to the valley floor and perhaps walk back to Lauterbrunnen on the valley floor. (There's also a Post bus if you are tired of walking.)
Day two I would take the hike above Wengen from Männlichen to Kleine Scheidegg train to gondola, gondola to top). Have lunch there looking at the Eiger, then walk down to Wengen and finally descend to Lauterbrunnen by train.
All of this is well explained in the Rick Steves' Switzerland guide. The book also has lots of advice on more adventurous activities, but by all means do NOT stay in Interlaken. Get up to the mountain valley. FYI, I like Lauterbrunnen as a base as then it is easy to go to both sides of the valley.