I'm not a Swiss expert, but I've been around that area a couple of times. Are the cable cars open at that time of year? If so, rather than the train to Kleine Scheidegg, you could take the cable car to Männlichen, next the cable car down the other side to Grindlewald, and then transfer by bus to the cable car up to First. You'll get views into two valleys that way. The trails are usually closed at that season, snow, mud, etc. You can return to the Lauterbrunen Valley the same way or take the train. This suggestion is based on the cable cars running in May.