The first story is "A Switch in Time" in which Billy is granted his wish to be older, but it comes at a cost!
The second story is "The Wizard of Phonograph Hill" and featured Captain Marvel and Dr. Thomas Kilowatt (this was his first appearance in Cap's comics).
The final story is a golden-age adventure from Marvel Family #4 (August 14, 1946) entitled "The Witches' Tale."
I love the cover of this comic featuring the Marvel Family drawn by C. C. Beck. While Captain Marvel was still the main focus of the comic series, Mary Marvel and Captain Marvel, Jr appeared frequently in the comics as well!