I think it's fair that an age-appropriate adaptation of Huck Finn should have language edits that remove terms that, given the lack of social education, a young child could misuse in an offensive way.
The original should be the original, for a great many important reasons.
It should be expected that, at a certain point, someone who enjoyed Huck Finn as a child in adapted form would seek out the original. By this time the reader should either be already educated about the social issues surrounding certain terms, or be prepared to learn about them, with the book as a useful aid to that.
Since that "certain point" will occur for different people at different times, and it's entirely subjective as to when that is, it makes sense to allow everyone to make their own decisions.
So, while I generally follow the same course you do (go ahead and introduce the archaic language, and use it as a discussion of how the meanings of words and social values change over time), I certainly understand anyone who takes a different approach.
