I would get them off of it. It will lead to unhealthy mice that you are feeding to your snake, and the snake will get unhealthy as well. The oils in the pine shavings cause kidney and lung damage, and you won't see adverse side effects until it is too late. Mice and rats don't usually show signs they are sick until they are very close to death. It's their survival instinct.
Pine should only be used for horses, who are 6ft off of the ground, and only have to touch it when they are in the stall. Mice are about 1/2" away from it, and have to touch it all of the time. I would get some aspen, as it is just as cheap as the pine, and won't cause any adverse reactions.