The Spiderwick Chronicles

Of the three Grace children, Jared has always been thought of as the troublemaker. So when strange things happen after his family's move to a relative's dilapidated estate, sister Mallory, twin brother Simon and their mother assume that Jared is behind it all. However, magical creatures roam the grounds, and they all want a special book that Jared has found: a field guide to fantastic creatures, penned by Arthur Spiderwick.