Son sell books, use new or old account?

Hi all. Thanks in advance for your advice. My son wants to sell books to save money for college; the whole family is giving him their hardcovers. I have an old personal seller account going back to 2008 with a great rating but only about 20 sales. I have not sold in seven years. So the question is what’s the best setup for him. Should I convert my account to a brand so I can add him to my store, or just set him up with a new account? And can he sell as a child on my family plan, or does he need a new account ( I think the latter, according to Amazon)? I could even give him my account, but I want the money he earns to be his (and not to mess up my recommendations etc). What is the best setup to handle the income he receives? In the past I just left it in Amazon because I bought enough stuff. I assume we’d link it to his personal savings account.

I asked Amazon, and their support person kept missing the point of my questions and I got tired of trying to explain. Thanks again!