Brian P. Cleary 
They’re There on Their Vacation [PDF ebook] 

Meet the Tuckabees. They’re going on vacation. But not an ordinary vacation. They always choose the wackiest, weirdest destinations for their family trips. This year their stops include visits to the world’s largest underwear, a narwhal petting zoo, and the amazing Cheezie Popz factory. No matter where this family goes, they’re sure to have tons of fun when they get there. Come along for the ride-and along the way, learn to tell apart they’re, their, and there. These words sound alike, but they’re different in meaning. Figure out how to keep them straight as you join the Tuckabees on their adventures.