<<"As for our interest, we are at Swiss solely for the nice natural views. ">>
Of the places that you have listed, you will find those nice (and scenic) natural views most easily in the Jungfrau region, Zermatt, and the Lake Lucerne area. Also, the north-eastern part of Lake Geneva near Montreux (Lac Leman.)
Although Geneva is on the beautiful lake, which is nice for a boat ride, the city itself is not really a scenic location in the sense of those other three. Montreux offers the vineyards and mountain railways nearby, especially Rochers de Naye. The mountains come right down to the lake there. The vineyards near Lausanne are also nice, especially in the harvest season.
The train mentioned in that last link, from Vevey to Puidoux, is a short and scenic ride. Depending on your ability or interests in walking/hiking with a two year old, walking in the vineyards can be enjoyable. The terrain is definitely not level. ;-)
www.switzerlandbyrail. com/trains/scenic/lava ux_wine_train_vevey_ch exbrex.htm
The best part of the Golden Pass Route is the line above Montreux, especially to Montbovon, on the way to Zweisimmen, thence to Interlaken. You might enjoy simply riding from Montreux to Montbovon and return, or deviate from the Golden Pass route and take the longer route onward to Gruyeres from Montbovon and return by (for example) Bulle, Romont, Puidoux, Lausanne, Geneva.
map.search.ch/Gruy%C3% A8res?pos=562144,154944&z=8& poi=zug
Zoom in for the rail lines; I have turned on an overlay under Points of Interest/Traffic/ railways that shows the train stops.
The short stretch of track as you leave the tunnel at Puidoux and go through the vineyards toward Lausanne , including towns like Grandvaux, is a very striking and beautiful view, best seen on a clear day with the Alps in the background. There is a joke popular in the French speaking regions, that once someone from the north of Switzerland (the German -speaking regions) sees that view, they throw away their residence permits and move to the lake shore region.
You will be on part of the Golden Pass Route when you travel from Luzern to Interlaken via Meiringen. That section is called the Luzern-Interlaken Express. It is a pleasant ride, with some good views.
We have spent many days in the area around Lake Lucerne. In German -der Vierwaldstättersee. And, as you have figured out, since Luzern is in the German-speaking region, the signs will show the spelling with a "z."
This link shows some views around the southernmost part of the lake, as part of a description of a hike in that area:
Attached are a few pictures from near Luzern itself, or, around the lake. One show my 8 year old granddaughter absorbing the Lion of Luzern...it is a page from a photobook that I made about our trip there in 2009.
Zurich is described here:
It is my favorite city in Switzerland, but not for scenery. Culture... museums, music, etc. It takes a while to begin to find your way into the rewards of Zürich. The old town, on both sides of the river, offers some nice walking. There is an excellent bus and tram network.
The southern part of the lake, near Rapperswil and Hurden, is peaceful and attractive. It is not a usual tourist destination. Three pictures attached.