Just my two cents added here.
Technically a GFCI does not work off of a ground wire at all. One is not even needed for it to function correctly. The functioning of a GFCI is as follows: the current going into the GFCI must be matched by the current leaving the GFCI by the nuetral (grounded)wire. If there is a difference between 4 to 6 milliamps then the GFCI will trip. This is why many 2 prong recepts are replaced with a GFCI just for safety and not for the equipment ground. The difference is telling the GFCI that amperage is missing and going somewhere it should not be going to.
As far as using a GFCI breaker for the kitchen that is not necessary and expensive. Replace the 2prong recept with a GFCI recpt and place the label provided with the GFCI "GFCI Protected" "No equipment ground"
Hope that helps
