Another vote for the Leupold Yosemite in 6X as the clear best choice. Nothing wrong with the 6X Katmai as child size with good ergonomics but getting to be expensive enough that there are equally good or better at the higher price point.
To that I would add an eye test for the child as I wonder how good his unassisted vision might be. I'm prejudiced as when I asked my own mother for glasses she said don't be silly you're much too young to need glasses but it wouldn't hurt to know.
