Krakow is a wonderful destination. The old walled city, the castle, the main square are worth at least couple of days on it's own.

The Nazi concentration camps of Aushwitz/Birkenau are just an hour outside the city. Do plan a whole day, just be prepared. It's a very sobering place. You don't want to plan any fun activities for the same evening.

Your hotel should be able to arrange a private or group tour in your prefered language with a pick-up and drop off at the hotel. If you prefer to do it on your own, then a rental car, taxi, bus and I believe a train are all available options.

You may also want to visit the Salt mines at Wieliczka. Amazing tour.

Jasna Gora Sanctuary in Czestochowa may be worth a visit as well. It's a national shrine of Poland. Many historical stories about Poland are associated with the sanctuary, including the legend of intervention by the Virgin Mary (Our Lady of Czestochowa) and saving Poland during the Swedish siege of Poland in 17th century. Pope John Paul II made many pilgrimages to the sanctuary before and during his papacy. General Casimir Pulaski, a future hero in the American revolution also used it as a fortress when fighting Russian invaders in the 18th century.

http://www.krakow-info.com/index.htm

Can't help with Starwood properties in Krakow.