Alexa, age 7, and I are reading a book called The Little Penguin. Do penguins eat seals? (We hope not...)

No, but there are seals that eat penguins.

Leopard seals will cruise off the coast of a penguin colony, waiting for an unsuspecting penguin, particularly an inexperienced juvenile, to enter the water. The leopard seal then pounces on its victim, flaying it by thrashing it against the surface of the water.