Advice for JK Rowling

I've been reading the Harry Potter books to Owen, and just before our trip to Whistler we reached the third task in the Tri-Wizard Cup from book four.  Harry and Cedric Diggory had competed with each other, but also helped each other and showed wonderful sportsmanship throughout the competition. When they decided to grab the Goblet of Fire together in order to share the victory, Owen felt a deep sense of satisfaction with the story.

That's where we left off before our ski trip, and I was a bit nervous about what was coming, so I warned Owen that the story was about to get much darker, but he insisted we continue reading when we got back from Canada.  Well, we read the next chapter tonight, and despite Owen making up an alternate version where Cedric wasn't killed, but instead awoke from the avada kadarva curse, crawled back to the Goblet of Fire -- which was still a portkey -- and grabbed it to transport himself to safety while Voldomort and Wormtail were distracted by Harry, Owen couldn't sleep and decided we needed to chat.

Dad, why would the author kill Cedric, didn't she want to make more money?  If she wants to write more Harry Potter books after this one, and she wants people to buy them and read them, she shouldn't have killed Cedric, because no one will want to read more of her books if she kills good people like Cedric.

Owen is a very gentle soul, and I think we might want to wait a bit before reading the rest of the series...