We visited Krakow and made it our hub for 7 nights, August 28 - September 4, with side trips to Auschwitz, Czestochowa, Wadowice, and the Wieliczka Salt Mine. All were outstanding and worthwhile. We stayed at the boutique Leonardo Hotel, between Old Town and Kazimierz, and it was excellent for a leisure traveler; its walkable location gave easy access to sites, shops, and restaurants of each district.
We splurged and hired a local driver, mentioned in the Rick Steves Guidebook, Andrew Durman ([email protected]), who assigned his associate, Karol, for all side trips for our convenience and comfort. We could not have made a better decision. Karol is professional, friendly, and fluent in English. He helped us a few times in Auschwitz, Czestochowa, and Wadowice with the language barrier. Additionally, he offered local recommendations for restaurants and things to do in Krakow, including "hidden gem" restaurants, which complemented the information from the Guidebook and the various Facebook groups we surveyed in advance.
You won't be disappointed spending 4 or more days in Krakow. Good luck!