The Marvel Family are featured on the cover of Shazam! 3 (June 1973), but only appear as a group in the third story in the issue, once again a reprint.
O'Neil and Beck open the issue with a story that shows us Billy Batson as an adult.
Billy is dismayed at still being a kid. For one thing, he has been around for 20 more years than he looks, although in suspendium. For the other, he is from a different era, and just finds he cannot talk or relate to people who are theoretically his own age.
He goes to visit the wizard Shazam, and requests that he be made an adult. Shazam grants this, but warns that it might have an effect on Captain Marvel.
Sure enough, it does. When Sterling Morris is threatened by an evil magician Captain Marvel tries to go into action to help him, but is incapable of controlling his body.
So he resorts to just beating up the magician as the adult version of himself. In this body, Morris doesn't recognize him, and neither does Freddy Freeman. Freddy is Captain Marvel Jr in his other identity.
Things are back to normal for the second story, by Maggin and Beck. Once again this is meant to be funny, and isn't. It deals with an Edison-like inventor, Professor Kilowatt, who announces that he has made an amazing new invention, but won't say what it is.
Everyone wants this new invention, and Captain Marvel spends the story protecting Kilowatt from thieves and spies. It turns out to be an anti-gravity machine. Which is ok. But not a big payoff.