Detectives in Diapers: The Mystery of the Aztec Amulet — Duane L. Ostler

Flo and Mo are not ordinary babies. Although they are only fourteen months old, they can use a computer, trick any mindless adult they want, and help their goofy detective father solve baffling crimes. Then a mysterious girl comes to their father, claiming that her grandmother has disappeared. Will the babies' superior brains be able to solve the mystery and save their bumbling parents?