Some basic scripting is probably still a good starting place for younger kids to wrap their minds around syntax, basic constructs, etc. Dropping them in the DOM right away is probably in the deep end, too much, although I'd agree getting them there quickly opens a lot of fun and practical doors faster than almost anything else.
edit: Second the suggestion of Python below, even if it's just for a few months to learn the basics of coding in general. Pivoting a few months in to a new environment is also hard in and of itself, but that's the path I'd go. As a little bonus, then you don't get too stuck in one way of thinking :)
You under estimate kids. You all are under estimating them. 10 year olds figure out how to modify mods written in C++ for games they love. Given interest, they will get it. And the web is what has their interest today.
No I'm thinking for like 7-8 year olds. I was doing C++ at age 11, but it was substantially easier because already had a few years of Pascal under my belt.
edit: Second the suggestion of Python below, even if it's just for a few months to learn the basics of coding in general. Pivoting a few months in to a new environment is also hard in and of itself, but that's the path I'd go. As a little bonus, then you don't get too stuck in one way of thinking :)