Should we get a Swiss Travel Pass, Half Fare Card or something else?

My husband and I will fly into Zurich on April 27th. We will stay 3 nights in Lucerne, one in Zermatt and 3 in Wengen then on to Germany. We will be using the train for transportation probably every day. When we are in Zurich we might take a boat around the lake and when we are in Wengen we will want to see Interlaken, Grindelwald and maybe a few other little toens.