The Radisson is lovely - I stayed there a couple of years ago just after it opened. A Sheraton opened a few months after my visit - not sure what that is like. The Radisson is a good bet, though, as its a short walk to both the castle and the central square. There is a Holiday Inn on the other side of town, but it looked to be getting on a bit.

There are two big days out you can do from Krakow, to the old salt mines (which I didn't do, but are highly regarded) and to Auschwitz (which I did do, and which you can do on the train if you don't want to pay £50 for a taxi). Out Fri AM, back Sun PM is probably best if you want to squeeze in one of the days out, Fri PM to Sun PM is fine if you're not leaving Krakow.