Hi screamingeagle247 and welcome on the forum
Better take trains. With a Swiss Pass or a Swiss Flexi Pass you can get a free family card which allows your kid to travel for free as long as they travel together with you.
After arrival at Geneva I would take the train from the airport railway station to Vevey or Montreux - www.montreux-vevey.com - and spend my first time there. For things to do see the Top Questions about Montreux (TA Montreux forum).
From Montreux you could take the goldenpass line (no need to take the tourist train, any train will be great) to Lucerne. On www.sbb.ch/en input from Montreux to Lucerne via Gstaad, press the advanced search button and input via Bruenig-Hasliberg. This trip will require a few changes due of technical reasons but this is one of the most scenic railway lines of Switzerland.
Get a lot of information about the Lucerne area (I think this is where you would like to go as you posted in the Lucerne forum) at www.luzern.com and on the Top Questions about Lucerne (upper right side of your actual screen).
From Lucerne it is easy to travel to Milano (often with an easy train change across the platform at Arth-Goldau).