Did she say outright that the "fairy-like" stories were for kids? White American society tends to package Native stories for kids (because that's who "we" expect fairy stories to be for), but inasmuch as one can say that Native stories are age-specific, my understanding is that most Native stories are "for" adults.

:: I find myself wanting to know if the Dakota and related tribes were the template for the stereotypical Indians of westerns and early cartoons. ::

Yes. The Indian stereotype is a Plains Indian: the classic cigar-store Indian is an example, as is the Mutual of Omaha logo. The stereotype of all Indians being Plains Indians is older than western movies -- I have the impression it was popularized by Buffalo Bill's Wild West Show (which featured many famous Plains Indians as performers, as well as doing re-enactments of the battle of Little Big Horn).

(BTW, totem poles, which get mashed into the stereotype from time to time, are not Plains -- they're northern Pacific coast.)

Oyate's review of Brother Eagle, Sister Sky is a contemporary example of the ubiquity of that stereotype. The book purports to be version of Sealth's famous speech, "Who Can Sell the Air?" Sealth was Suquamish, which is a Puget Sound tribe, and is the man Seattle was named after. This is the only known photo of him. And yet the author used a painting of this photo for the cover of the book: Two Moons of the Cheyenne in his Plains regalia. When called on it, the author/illustrator protested that she had gone to great lengths to make the illustrations authentic, having used actual Sioux to sit as her models.