What happened to the family that was in the Arch with Percy? Chapter 14

The family survived. The mother was brought out on a stretcher and told that the rest of her family was fine.

Behind us, a cop shouted, "Gangway!" The crowd parted, and a couple of paramedics hustled out, rolling a woman on a stretcher. I recognized her immediately as the mother of the little boy who'd been on the observation deck. She was saying, "And then this huge dog, this huge fire-breathing Chihuahua - "

"Okay, ma'am," the paramedic said. "Just calm down. Your family is fine. The medication is starting to kick in."