Krakow sites

At that time of year I don't think you need to pre-book any sites. I booked an Auschwitz tour in advance, but that's because I didn't want to mess with getting there on my own. I thought Krakow was a great city. Enjoy.

You could keep track of the Auschwitz and Schindler Factory Museum tickets online, maybe start about a month out, and see if they seem to be selling. I'm going the first week of September and got the last ticket over a week ago for the day I wanted to go to the Schindler museum. I assume October will be less busy, but if you have specific days/times in mind, probably best to keep track.

When I went in early October last year, tickets for the Schindler Factory were sold out online for the next few days. I was able to get a ticket for 3 days later. Fortunately I was still in town.

I've read that there are some same day tickets made available if you get there early.

Mondays are free, but you have to book tickets. Mondays usually get fully booked. The price is not expensive so as long as you don't have to go on a Monday, it shouldn't be a problem.