E. Nesbit

The film opens in a happy, comfortable upper middle-class home in Victorian London. One night the three children see their father usher two strangers into his study. After an argument he leaves with them and does not return. They and their mother fall on hard times and eventually move to a cottage in the country... (imdb)

'It' is a Psammead (voiced by Eddie Izzard), an ancient, ugly and irritable sand fairy the children find one day on a secret beach at their uncle's mansion. It grants them one wish per day, lasting until sunset. But they soon learn it is very hard to think of really sensible wishes, and each one gets them into unexpected difficulties. Magic, the children find, can be as awkward as it is enticing. (imdb)