Pick a Heinlein juvenile, almost any Heinlein juvenile...
Rocket Ship Galileo, perhaps? From the Heinlein Society link:
In Rocket Ship Galileo, Ross, Art, and Morrie help Art’s uncle, atomic scientist Donald Cargraves, build a rocket ship and fly it to the moon. There, they discover a Nazi stronghold (this was 1947) and thwart an attempt to resurrect the Reich.
The Rolling Stones? From Wikipedia:
The Stones, a family of "Loonies" (residents of the Moon, known as "Luna" in the book [from the Roman goddess]), purchase and rebuild a used spaceship and go sightseeing around the Solar System.
The twin teenage boys, Castor and Pollux, buy used bicycles on Luna to sell on Mars, their first stop, where they run afoul of local regulations but are freed by their grandmother Hazel Stone. While on Mars, the twins buy their brother Buster a native Martian creature called a flat cat, which produces a soothing vibration, as a pet.