You, or his parents, or his wife, can add him as an authorized user on your
Oldest credit card (assuming you don't carry a balance) you don't actually have to give him a card so he won't actually use it. He can just piggy back on you credit.
Also they should max out the subsided portion of their student loans, even if they don't need it, they can save the money and pay it back 6 months after graduation literally for free.