If you go, I suggest you add Vienma and Prague. If you go to Krakow you can bogus to Auschwitz in an hour.
And if you’re in Krakow, definitely do the Wieliczka Salt Mine.
Very much need to go to Vienna, to see the Schonbrunn Palace, because my great great grandfather was the Head drum Major of the Austro-Hungarian Army and loved Emperor Franz Josef and his family.