Basically he wanted to show that in order to keep his sons alive he wanted to insure that their wardrobe would keep them out of trouble. They don't wear t-shirts, there are no shirts with any lettering or they wear mostly wear khaki pants clothes that he hopes wouldn't make them look suspicious.
He made a splash late last year talking about how he hoped their "elite upbringing" would protect his children from discrimination. And here in lies the rub, some of the comments in that video suggested that they wore the same types of clothes and still got harassed by police. So it's possible the same thing could still happen to Mr. Graham's children.
He resides in New York so it's now like he lives in Harlem or whatever black areas exist in NYC. Perhaps his kids wouldn't be targets in whatever upscale area they reside. Of course in that column, he said that one of his sons had been called the n-word by some random strangers.
Unfortunately the human need to point out a minor difference such as skin color rears its ugly head. They had to call this kid out because he's not white and it didn't matter if he in fact didn't fit that stereotype. It was not about that kid, but about their need to just express some juvenile feelings they have towards a group of people. They didn't see a kid who came from money they saw a black kid and targeted him.
BTW, I wouldn't write this to criticize Mr. Graham. He's already getting attacked on social media probably for having some money and being Black. He doesn't have the wrong idea either probably his only deal is showing he has the same concerns as most other Black fathers.