It would be a tap on the shoulder. I often see kids who play together at the fast food place while their parents eat, then have a coffee. The kids crawl through tubes and jump in the pit of plastic balls. They yell, they scream, they invent games, and they never ask each other for a name.
"Hey, let's go back to the top" says one. "Okay" yells the other.
I think names are only important in the grown-ups' world.