Interlaken to Kleine Scheidegg (above Wengen) takes about an hour and a quarter by train. From there - you can get off the train, clip on your skis and just go - you don't need to take another cable car or lift, you can head off down to either Wengen or Grindelwald. A half day pass is generally available after 12.15 (or could be 12.30). It's a few chfs less than the full day pass, and you should be able to buy it integrated with the train ticket in the train station in Interlaken. But just to note the lifts will close by 3.30 until about Feb when the days start to get a bit longer again (but the train will run till late evening).
The nearest ski areas to Interlaken are Grindelwald, Wengen and Murren - all are a rail journey away from Interlaken. It would take you about one hour (at least) to get from the centre of Interlaken to the pistes.