Lawdog is a lawyer. As well, quite a few of us have spoken to lawyers on the subject of replica firearm. Don't know who has actually talked about possession by minors, though. Very few lawyers would be able to reliably comment on the subject anyways, it's rather off the beaten path.
Finally, as people have said, there is no law against possession of replica regardless of age, while unauthorized acquisition and transfer is illegal regardless of age. You don't need to consult a lawyer to know what laws exist and doesn't, you can look it up yourself.
"The Bird of Hermes is My Name, Eating My Wings to Make Me Tame."