The Enid Blyton Secret Series
The Secret Island - pt. 1
S1 E1:
Peggy, Mike and Laura are staying with their horrible Aunt and Uncle while their eccentric father, Thaddeus sails around the world, accompanied by photo journalist Charlotte Clancy. But in the aftermath of an unexpected storm, Thaddeus and Charlotte are presumed drowned and the children's Uncle and Aunt see this as not only the perfect chance for inheriting Thaddeus's estate - but selling it.