We are flying in and out of Rome ( tickets already purchased) and will spend 3 nights there on tail end of trip
We have a week more to play with not counting ROme so are going to Varenna from Rome ( I guess via train) and spending a few nights there, so basically we then want to cross into Switzerland and spend 2 nights before heading back to ROme again
if we did stay in Pontresina or Samedan rather that St.MOritz what is the best option for getting around the town?? Rental car??
Suzy, if you don't mind me saying so, you have a North American's fixation with flying and cars. You are "beginners for sure!!".
With hindsight, it would have been better to fly into Zürich and out of Rome, use train to link all the places in between together.
You can still do this, as soon as you get to Rome, either the same day or the next, fly north to Zürich. You have unfortunately wasted time by going via Rome. As soon as you land, get a train from the airport to Chur. If you land in the afternoon, overnight in Chur. Next morning on to Pontresina or Samedan (first part of Bernina Route, including the famous Landwasser viaduct, click here for photo)
If you land early enough, go direct via Chur to Pontresina or Samedan.
1 or 2 nights in Pontresina or Samedan.
In towns either walk or use local transport (buses), you do not rent a car just to get around inside a town (North American thinking). Possibly a taxi from the station with your luggage. Small tourist towns are not designed for cars, they are optimised for people without cars.
Next day, 2nd part of Bernina route, via Tirano, to Varenna
Finally train Varenna --> Milan --> Rome. If you have spares days, add an overnight in Florence, on the route.