Mole, Ratty, Badger and Mr. Toad, the characters Kenneth Grahame conjured up for his son 100 years ago have scampered across printed page, silver screen and legitimate stage. Now the four friends of The Wind and the Willows arrive on South Coast Repertory's Julianne Argyros Stage in a new musical adaptation by Richard Hellesen and Michael Silversher. For the final staging in its inaugural season of "Theatre for Young Audiences . . . and Their Families," South Coast Repertory combines its decades-old program for new play development with its new program for family-oriented theatre. The Wind in the Willows was commissioned from playwright Hellesen and composer/lyricist Silversher. Art Manke directs. The three-week run of The Wind in the Willows begins with three low-priced weekend previews (Friday, June 4 at 7 p.m., Saturday, June 5 at 4:30 p.m. and Sunday, June 6 at 2 p.m.), followed by two weeks of weekday school performances (Tuesday, Wednesday, Thursday at 9:30 and 11:15 a.m. each day) and weekend public performances (Friday at 7 p.m. and Saturday and Sunday at 2 and 4:30 p.m.). Two Saturday performances have been added: June 12 at 11 a.m. and June 19 at 7:30 p.m.