Leviathan

This steampunk alternate WWI history makes a great family road trip book (Alan Cumming narrates the audiobook). Aleksandar is a Clanker, part of the Austro-Hungarian force of steam-driven machines and guns. Deryn is a Darwinist, part of the British force of genetically modified animals, including the Leviathan, a whale airship. When they cross paths, the two foes develop an unlikely friendship and travel the world on the adventure of a lifetime.