http://www.space.com/36515-how-would-nasa-search-for-extraterrestrial-life-on-enceladus.html If the venting is taking place at the same location year after year then the heated water that is escaping from the surface of Enceladus could mean that the ice itself and directly underneath of the frozen ice could in fact be teaming with life as the heated water would create pockets of plankton like life that larger feeder microbes could feed off of. I also suspect that the underside of the area of the frozen surface where the eruptions are taking place could have a form of algae like growth that could also feed off of the microbial plankton. Plant like life could take root on the underside of the frozen ice where the plants roots would travel to surface or close to the surface of Enceladus to a point of being able to take in the light from the Sun that is able to penetrate the frozen surface where photosynthesis could occur. Breathable oxygen might also be trapped in the vents that then finds its way out into the rest of the frozen ice allowing for a much larger under surface area where animals have burrowed into the frozen ice and might be able to survive much like seals do in the arctic.
If snow acts as a thermal insulator similar to Eskimo igloo's then the thick frozen ice of Enceladus would also act as a thermal insulator for any heat being released from the core of Enceladus. However because there is it not a widespread collapse of the surface into the ocean under Enceladus then the thermal vents on the ocean floor of Enceladus might only be present in one location. Even if the thermal vents were small and numerous across Enceladus' ocean floor the total area heated by the thermal vents would greatly increase the temperature of the ocean of Enceladus which would result in surface collapse of ice that would be similar to an ice shelf breaking off of an ice pack at the North Pole.