Help for a family of 5

Hello- My wife and I will be visiting Switzerland with our three boys (ages 18,15, and 10) this June and I am thoroughly confused on what passes, cards, etc I should purchase if any. We are renting a car in Zurich and will travel to Lucerne and then onto Interlaken. In both places I hope, weather permitting, to travel up to Pilatus and the Jungfrau Mountains. We will then depart from Interlaken via train to Venice. Unfortunately we are only in Switzerland for 4 days. Should I purchase a pass in order to get discounts on the mountain railroads, boats, gondolas, etc or simply pay for the tickets individually? Will a Swiss Family Card help reduce the costs of those tickets for two of my kids and do I have to buy a pass to get the Family Card? Will the Family Card and/or Pass help me at all with the price of the tickets from Interlaken to Venice? Thanks in advance for any assistance.

Thanks so much Arno for the the response. I will look into that option and price it out. Have a nice day.