PB Kerr
The Akhenaten Adventure, The Blue Djinn of Babylon and The Cobra King of Kathmandu.
Upon the removal of their wisdom teeth, twins John and Phillipa Gaunt discover they have strange magical powers. Sent off to their Uncle Nimrod, the Gaunt kids learn to use their djinn powers. With lots of historic background, this series is a cross between Indiana Jones and Harry Potter with touches of Arabian Nights (literally) thrown in.