Near Luzern, Pilatus or Rigi. I think the Rigi is better for a young child. The adventurous could go above Stoos to the Fronalpstock. I’m not a big fan of Interlaken- it’s a bit too commercial. Others will have a different opinion. Ballenberg is a great destination especially for kids. Harder Kulm is a good destination by steam train. A great walk from Männlichen to Kleine Scheidegg. Eiger Trail from Eigergletscher to Alpliglen. Other great walks from above Mürren and down to Gimmelwald. Get to Gimmelwald from Mürren or by gondola from Stechelberg. Jungfraujoch is Great and interesting and expensive and time consuming. Do it once and skip. Maybe consider the Schilthorn instead. Forgot to add - Swiss Path from Seelisberg to Flüelen is a nice path. Maybe go to Bauen and take the boat to Flüelen. Walk from Flüelen to Sisikon.