Warlock and Son — Christopher Stasheff

Even the son of a warlock gets restless sometimes. And when Magnus sets off to see the world, his father, Rod Gallowglass, and the robot horse, Fess, can't resist trailing behind. Someone's got to protect young Magnus from spellbinding witches, enchanted maidens, and jealous husbands. But when it comes to real danger--and growing up is on his own...