Sounds to me like you did "the right thing" as far as your son is concerned ;-) So now your his Hero. Probably would also be a good idea to let him (with a little guidence?) zero the scope "on his own", after all how else will he learn how?

A big part of being a parent is also being a teacher. Which was (and still is) one of the more enjoyable parts, at least for me ;-)

Glad it worked out well!