Once again-thank you all for your many useful suggestions!
Have done a bit more fine tuning and actually set our dates- we will travel in May 2016 rather than September.
We have come up with this plan- any comments, advice, suggestions are welcome-
Day 1 Fly to FRA- train to Wurzburg - 1 night- just get over jet lag
Day 2-3 Train to Nuremberg- 2 nights - day trip to Bamberg- pick up car as we depart Nuremberg to RodT
Day 4-5 Drive to Rothenburg - 2 nights- day trip probably to Bad Windsheim
Day 6 Drive to Fussen- 1 night arrive late afternoon- visit towns along Romantic Road,Weiskirsche en route
Day 7-8 Visit Ludwig castles in AM, drive to Garmisch- stay 2 nights- visit Linderfhof, Ettal, Oberammergau.
Day 9-11 Drop car in Garmisch- train to Munich- 3 nights with day trip to Dachau
Day 12-14 Train to Salzburg- 3 nights- day trip to Berchtesgaden or St. Gilgen
Day 15- Early shuttle to Cesky Krumlov- stay 1 night- depart next day on late afternoon bus to Prague. (We arrive in CK on a Monday so will need to stay longer next day to visit castle (closed on Mon))
Day 16-19 Prague 4 nights
Day 20-22 Fly to Amsterdam- 3 nights
Questions:
Car rental in Nuremberg- any advice? I’ve used AutoEuope in the past and happy with them- need an automatic so hope that by renting in a larger town that will be available (we had an issue with this in Italy -reserved compact automatic but only one they had on lot was a mini-van- we managed fine but would not like a repeat of that fiasco!)
Berchtesgaden or St Gilgen? Might be something we just decide on day of weather dependent.
I will post this on Czech forum as well- have a few questions about that portion of trip.
Thanks