Credit Card Bonuses for Addition of Authorized User

My son is turning 16 in two weeks and I would like to add him as an authorized user on one of my credit cards. I currently have 2 Capital One Quicksilver cards, a Discover it card, and an Apple Card. My son does not have an Apple device, so I’d rather not add him to that card. The Capital One accounts are my oldest accounts, but have a very low credit limit. My Discover card has a very high limit but isn’t quite as old as the Capital One cards.

Are there any rewards offered for adding authorized users to credit cards? Would my son’s credit benefit more from the age of my Capital One card or the limit on the Discover card? I do not currently plan on giving him a physical card yet, but likely will once he has a car for emergencies.

The reward is he gets a credit history. I added my daughter around age 17 or 18, and she built a good history. She was only allowed (by me) to use the card on a limited basis. For a long time she didn’t even physically possess it, then I gave it to her when she went to college. Then when she got a job, I removed her as a user.