I loath the fact that someone else is having to deal with the doctrine of hell being shoved in one's face. However, I have found something that has shut my family up for the past few months and it is the greek translation of the word hell in the N.T. It translates to "Gehenna" which was a trash heap outside the walls of Jerusalem. Bodies, criminals, and deformed or still-born children were thrown into it and the Romans would set fire to it every month. However, when the city was taken the trash heap was lost. Therefore, worrying about it now is rather foolish. And then I informed them of the Norse Goddess Hel and the underwotld that deity had dominion over, and this also has my family thinking. Of course, I have had to di it little by little. Doing it all at once was not productive. Of course, a person could offer them the gospel of the flying spaghetti monster and tell them that since they refuse it they are doomed to the freezer. Of course, you may not want to go that route.
Tell them they can't possibly know that.