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what about taking the Scratch implementation based on Pharo called Phratch into consideration?
It could be much more fun for a 10-year old than the much more powerfull Smalltalk operating system :).
I would try Squeak, Learning Programming with Robots . It's
what I used with my freshmen students at the University. Most of
them have no previous experience with programming. That, combined
with Etoys and Scratch worked pretty well. I don't know if there
is some image that can be run these days thought.