Eden's Gate by Leslie M Kuntz

Adolescents JoSamne, Qenan, and their sister Ahnwen are the great-grandkids of Adam and Eve. They search for missing sheep in a tropical mountain valley where they engage and flee several dinosaur species, cross a stormy desert, and experience altering pools and mazes while a mysterious traveler stalks them. They locate the Garden of Eden and the Tree of Life. Their very souls become in jeopardy when they approach the Garden of Eden.The gate is guarded by a Cherubim and Flaming sword.