On the family entertainment front, Mission-Improvable (Avery Schreiber Theatre, June 6-27) offers improv entertainment for youngsters 4-14. And Emmy-winning newswoman Katie Couric's book The Brand New Kid is the inspiration for a musical adaptation by the same name (South Coast Repertory, through June 14). Book is by Melanie Marnich, music is by Michael Friedman, and both collaborated on the lyrics for the show about a common problem endured by children -- dealing with teasers.