"Well, son," she says, "these are ... er,? balloons!? And when you die, they inflate and float you up to heaven."
Incredibly, the boy appears to believe this explanation and goes off quite satisfied. Two days later while his mother is making tea, he rushes into the kitchen "Mommy, mommy, Aunt Eliza is dying!"
"What do you mean?" asks his mother.
Well, she's out in the garden shed, lying on the floor. Both her balloons are out, Daddy's blowing them up, and she keeps yelling "God, I'm coming! God, I'm coming!!!