We were there two weeks ago.
Church of the Virgin Mary is spectacular and listen out for the trumpeter in the tower (every hour!)
We did Auschwitz and the Salt Mines on separate days, it would be a lot of walking for one day unless you are super fit. We were picked up at 6am for Auschwitz and we’re back in the Square by 1.30.
As someone else said, there are 800 steps down in the mines, 400+ at the beginning on a tight winding staircase. No option to stop. It was worth it though and there is a lift back up at the end (although still a bit of a trek when you think the tour has finished!)
Starka is a fab restaurant with live music after 8pm on Wednesdays, we booked before we went, but you will get great food practically anywhere!
There is a church on Grodzka where they have classical music concerts in the evening if that is your kind of thing. We stumbled across it whilst walking from the main square to Wawel Castle.
Ghettoes heroes square and the remains of the ghetto wall in the Jewish Quarter were also worth a visit.
Enjoy, Krakow is absolutely beautiful.