The invisible boy - Sally Gardner

THE INVISIBLE BOY: when his parents are lost in space, Sam is left, heartbroken, in the care of the horrible Hilda Hardbottom. Then he finds a tiny spaceship in the cabbage patch and meets a little alien called Splodge. How Splodge makes him invisible, and how Sam uses his new talent in his darkest hour, makes a touching and extremely funny story with lovely memorable characters.

THE BOY WITH THE MAGIC NUMBERS: when Billy Pickles' dad leaves home to live in New York, he gives Billy a moneybox. Billy's not sure where to put in the money, and not sure why his dad has left.
Then Billy goes to New York to visit his father and his Italian grandmother, and discovers the secret of his magic moneybox. In a wonderful adventure, he takes Mighty Mamma on a helicopter ride, cracks open a safe, solves a kidnap mystery - and gets to know his dad again.