This certainly has gone tangential to your original question. Going back to the beginning, for the 10k and the 4.7k a 1/8W current rating would be enough.

I don't see where you said what PIC you're using. I looked at the 12F683 and see where it would be able to clamp 20mA at GPIO input. You may be able to use one resistor of sufficient size to take advantage of PIC internal circuitry to clamp that 12VDC but the datasheet shows only +.3V over VDD. To me a better way would be the voltage divider scheme you first posited.

I hope you finally got your answers.