They retain their powers.
They are now part of the Shazam Family, and are their primary members in the comics.
Mary: She shares Billy's secret, and by saying "Shazam!" she can gain a superpowered form similar to the traditional Mary Marvel in a red uniform.
Freddy: He shares Billy's secret and by saying "Shazam!" can gain a form similar to an adult version of the traditional Captain Marvel, Jr in a blue uniform.
Eugene: Eugene can share Billy's power by saying "Shazam!" and become an adult Shazam-powered version of himself in a silver uniform. He has the added power of technopathy: the ability to control and manipulate technology via thought.
Pedro: Pedro can share Billy's power by saying "Shazam!" and become an adult Shazam-powered version of himself, resembling a powerlifter in a green uniform.1 In superhuman form, Pedro has extra amounts of super-strength compared to the rest of the Shazam Family.
Darla: Darla can share Billy's power by saying "Shazam!".1 She wears a purple uniform, and her speed abilities are amplified, making her faster than the others.
He (probably) can't share his powers with others.
The comics have other characters belonging to the family, somewhere in the future, or other universes. It isn't specifically shown whether Shazam could share his powers with other characters in the movie.
However, we can theorize that the broken staff metaphor makes it clear he cannot. From now on, in the DCEU, these are the only characters sharing the powers of Shazam.