i have had excellent trips to warsaw in the last few years, a couple of days will be sufficient, and there are plenty of things to see. why gdansk ? shipyards a thing you like are they ?

as for auschwitz, it is easily reached by train from krakow, and it is a small enough town to walk through. the guided tour, in my experience, is annoying, better to contemplate the horrors on your own, rather than be interrupted by the un-informed banal questioning of other tourists.. the only thing is the train station is named in the polish name now, so best look it up in the guidebooks.

krakow is lovely, just make sure you stay in the old town itself.