Gift ideas -- art, literature, books for children; Stevenson anniversary editions; Treasure Island, by Robert Louis Stevenson. Illustrated by N. C. Wyeth. New York: Charles Scribner's Sons. 273 pp. $17.95.; Kidnapped, by Robert Louis Stevenson. Illustrated by N. C. Wyeth. New York: Charles Scribner's Sons. 289 pp. $17.95.

Parents and grandparents who are tired of giving youngsters plastic space toys and computer games will find attractive alternatives in these richly finished editions of classic adventure stories. They commemorate the 100th anniversary of the publication of ''Treasure Island.'' In reissuing Stevenson's works, Scribner's has remained faithful to their early editions illustrated by N.C. Wyeth. The same easy-to-read typeface and memorable pictures grace both books. It was to Scribner's credit that it chose Wyeth to illustrate Stevenson's ''boy's books'' in 1911.

Stevenson wrote ''Treasure Island'' for his 12-year-old stepson, and he hoped ''to steal some young gentleman's attention from his 'Ovid' '' with ''Kidnapped.'' Although both classics have youthful narrators, they are not childish books, but appeal to all who love a romantic adventure story. These editions are of an unmatched quality that will be treasured as heirlooms for the next century.