Making Reservation for Italy & beyond

I am coming (first time) to Italy with a Family of 4 (including 2 kids of 6 & 9) this June. I have a Eurail Global Pass & my travel plan is as follows:

• June 23rd - Geneva to Rome
• June 25th - Rome to Florence
• June 27th - Florence to Munich
• July 7th - Munich to Milan

I would prefer Free or Low-cost travel on all the above routes. Now coming to my route-wise queries:

Geneva to Rome

This is the trickiest one & would really need your detailed guidance here. I have two options for this route:

• Option 1 (my preferred option if it can be executed, as with it I can also experience Bernina). Getting on Bernina Express from somewhere and reaching Tirano. Then take the regional Bus to Milan. Lastly, Travel from Milan to Rome on a regional train.
• Option 2. Take any available trains from Geneva to Rome.

Now coming to my questions related to this route:

1. Is Option 1 feasible? As to hop on Bernina, I first need to reach some point and do not know if I can reach in time to catch Bernina. I have no issue starting my journey early, but staying at some other location other than Geneva will be an issue.
2. If Option 1 is feasible, what all reservations etc I need to do?
3. In case of Option 2, please suggest trains/sub-routes to follow?

Rome to Florence

• I will take the free 3-hour train.
• Please advise on the reservation procedure?

Florence to Munich

1. Please suggest which trains / sub-routes to follow?
2. Also advise on the reservation procedure.

Munich to Milan

1. Please suggest which trains / sub-routes to follow?
2. Also advise on the reservation procedure.

Thanks