It is you as the adult who spotted the error, I'm guessing, not your son. Or maybe I'm wrong. Maybe your son came running to you, in tears, crying "Mommy, Mommy! It says here that Don Newcombe played on the Dodgers in 1960 and I know that that's not true! (From my extensive reading on late 50s and early 60s baseball history...!) Now I'll never be able to believe in anything ever again! Next I'm gonna find out Santa Claus isn't real...! Oh boo hoo hoooooo!"
Well..., maybe not. This is the sort of thing adult baseball fanatics care about -- not children.
The concept of "history being re-written" usually refers to big, important things like Holocaust denial -- not an obscure factual error concerning what year a certain baseball player was still playing or not playing on a particular team.
If you love the book, as you say, why make a stink over something so small?
Overreacting a bit? Children do like facts and details. In fact, one of the great appeals of the book are the many facts in it. Accuracy isn't a perk but should be a given. I'm sure the author would agree or would not have had a bibliography of sources.
Accuracy is important, and it's quite likely the author would agree with you. But it might also be accurate to characterize your focus on this particular and relatively minor error to be an "overreaction." Was it really worth creating a "forum" over?