Talk of little things. Okay. Ignore for now all the terrible shit that was going down and show his grandfather how to spend money. After all, they were Blacks.
Only problem was, he didn't know much about the little plastic cards, either. Wasn't like they used them in the wizarding world in 1981.
"Um, I'm guessing not. I think you just give them this card instead, at the stores. And see what happens?"