The correct answer is sentence 1 ("It all happened late one night after the family had gone to bed").
In this paragraph, we're presented with a narrow re-telling of one very simple sequence of events. Jack was in bed and remembered he had left ice cream in the car along with the groceries, then he got up and put it in the refrigerator so it wouldn't melt.
Opening the paragraph with an introductory statement including a phrase such as "It all happened" suggests a particularly remarkable or convoluted story is about to be told, which isn't the case at all. Quite the opposite, what follows is a very simple string of events. That's why the first sentence doesn't make logical sense in relation to the rest of the paragraph.
Hope it helps!