there are two things really about using printf in an interupt,the first is that you should avoid calling other functions from an interupt because your stack will quickly overflow, and secondly any print function is generally slow and you really want to keep interupts as short as possible.Apart from that good plan.I don't know about kiel but printf does usually use putc,i have used printf with a serial putc routine to send stuff over the serial bus.
maybe you should rethink the idea of using print from within an interupt,you can certainly use an interupt to fill a print buffer then call printf from your main routine.