Pretty sure you’re going to run into Fed law issues...
It’s and old WaPo article, but still, there is at least a link to the “exceptions”:
https://www.washingtonpost.com/news/wonk/wp/2014/08/27/in-30-states-a-child-can-still-legally-own-a-rife-or-shotgun/
Minimum Age for Gun Possession: Subject to limited exceptions*, federal law prohibits the possession of a handgun or handgun ammunition by any person under the age of 18.15,16 Federal law provides no minimum age for the possession of long guns or long gun ammunition.
*Exceptions: Federal law provides exceptions for the temporary transfer and possession of handguns and handgun ammunition for specified activities, including employment, ranching, farming, target practice and hunting.
I keep finding the same info on several sources (another would be findlaw).
You are correct as to Federal law on possession of handguns for those under the age of 18.
But minors may own something without possessing it. Parents normally are considered to be possessing guns in the home, including handguns, even if they are owned by minors.
As a common example, a minor may be gifted a handgun as part of an estate, but does not gain possession until they are 18.