Under the Sea
For sure Europa, and perhaps Ganymeade. While I m not sure how deap you would have to be for radiation purposes, these would be ideal since they are surrounded byu water. We sure know a heck of a lot about living under such circumstances, being that the military is able to provide power, air and water for nearly limitless amount of time for it submarines. The only constraint is the amount of food on board.
any suggestion on how to feed them?
-Justin Kelly