I'm not too sure about the PC status of the act of smoking, in isolation, but I would say that presenting yourself to kids as an educating figure who smokes is probably seen as less than PC to some.
Little different since one is an action, the other a state/symptom/result/outcome.
I guess there's an argument to be made against promoting/normalising activities that cause obesity, but I'd say current societal norms are set up to demonise smoking a lot more strongly.