Zurich to Rome 11 night itinerary with 5 year old very confused

Hi everyone! I’ve changed my trip itinerary a thousand times by now and my brain is fried. Please help me divide up my 11 nights between Switzerland, Florence, and Rome. Potentially Milan if needed to break up travel.

About us- 2 adults and a 5 year old. Safety and relaxation very important to us. We want to see beautiful sights, have great food, and access to local shopping. We will not be hiking or doing anything adventurous. One thing we really are excited about is Bernina express train but I don’t know how to fit that into our itinerary if we are on the western side of Switzerland.

Current plan-

Switzerland 4-5 nights

Florence- 3 nights

Rome- 3 nights

I am confused about where to stay in Switzerland and if we need to switch hotels at some point to make our way south. Or do we stay in one spot? Should we just forget about bernina express or is there an efficient way to make it work? And can we go straight to Florence or should we really be stopping in Milan for a night?

Everything I’m reading says to stay in Lucern and then go to Wengen and then to Florence. This wouldn’t allow for Bernina and would be a long travel day to Florence. But is it the right thing to do?

Any thoughts are appreciated! I am usually good at planning trips but this one has really tired my brain out. Thank you!

As