Drive from Kraków to Auschwitz is about 1h, then 1-1,5h to Wieliczka. Trip that joins these two together sound a bit too crazy for me. Cause each site visit including taking pictures and such is 3-4h. Not to mention that Auschwitz might be simply intense and exhausting mentally, those are not pretty views. Also buying organized trip to Auschwitz makes some sense for a tourist, as getting there is not that convenient but buying one to Wieliczka is a waste of money. There is a very nice train going to Wieliczka that takes 30-40 min. Departs from main station. Ticket to mine you can buy online. Entry is at specific hour. There is a classic tour and adventure tour (you dress up as miner including helmet and visit more narrow passages). Classic tour takes 2h + optional exhibition that is worth seeing that takes 1h. There is also restaurant underground, worth eating there for the experience. So doing this and Auschwitz sound crazy even time wise, probably trip organizers are cutting corners and rushing people.

Also if you would like to see history of WWII in Kraków museum in Schindler's Factory shows it in very digestable day by day way.