THANK GOODNESS there are still a few grown-ups wise enough not to put aside childish things. "Kids' Writes in the Nation's Capital" is a remarkable revue written entirely by area kids, and produced and performed by adults. It's a terrific introduction to what theater can be.

At the Kennedy Center Terrace Theater, the show is the centerpiece of the ninth annual Imagination Celebration, the national children's arts festival funded by the Kennedy Center and the U.S. Department of Education.

In 60 zippy minutes, "Kids' Writes" runs the full emotional range, touching fleetingly but tellingly on the bellwether issues of youth: parents and pets, the world and the weather, best friends and heroes, with plenty of whimsical nonsense in between.

The simple words, which were produced in creative writing workshops at Washington- area schools last year, are winningly brought to life by the Magic Carpet Band, an antic troupe of five actor/mime/musicians. They are more nearly magicians. Led by James Mairs, who founded the group of Californians in 1972, the friendly, energetic actors are remarkable mimes, and pretty good at making funny noises, too.

It's a sunny, funny show, but never saccharine or condescending. The young authors don't skip the sad and scary things about childhood -- their audience wouldn't buy it if they did. Though there are bad feelings to be faced in life, "you can't be sad forever," decides Samantha Metcalf, 10, whose poem "Sad" has been turned into a sweet, haunting song.

Other insights from the novice authors:

Joseph L. Hazward, 12, stalwartly describes "My Hero, Dad."

Janice Meerman, nine, speculates about why kids don't like the same things parents like: "My mom hates pizza and my father doesn't like McDonald's!" says actress Wynn White to a general cry of disbelief from the audience.

Jeremy Wade Anderson, eight, writes a why-not tale about playing hide-and-seek on a city street with a triceratops, vividly created by three performers in a mime demonstration that Mummenschanz could be proud of.

John Rousseau, a whiz at animal imitations, is also terrific in 14-year-old Andrew Maraniss' fantasy about a presidential speech that turns into a breakdancing State of the Union.

Carlo Grossman stars in 12-year-old Ryan Wilson's playlet about a brand-new rock singer, who, after a lot of wriggling and jiggling, gets stage fright when it's time to open his mouth and sing. When the audience welcomes him back, he returns triumphant with "I Know I Feel Good," while the rest of the troupe backs him up as a full-fledged rock band.

And Kate Zubritsky, 12, contributes a story about a boy who's sad about his funny name ("Frank Frizzo") till he meets a kid with an even funnier one, who tells him, "It's better than being ordinary."

It's all set to music and skits by the performers, who haven't changed a word or fixed a phrase. And as the skits and poems melt into each other, they gain in thematic strength, as in a section about things that happen -- or are imagined -- in the dark, like bad dreams and monsters under the bed.

"This show goes to show that kids can write," Mairs tells the rapt and remarkably unfidgety audience. "If you put your mind to it, who knows what you can do?" WRITE STUFF FOR KIDS

Public performances of "Kids' Writes" are Saturday at noon and 2 p.m., Sunday at 1 and 3 p.m. and April 13 at noon and 2 p.m. Tickets are $6.50.

The Imagination Celebration continues through April 13. Other shows include:

THE ELECTRONIC DANCE TRANSFORMER -- Also commissioned by the Kennedy Center, it explains dance to youngsters by describing the brain and body as a computer system. There are two free performances in the Theater Lab Saturday at 11 a.m and 1 p.m. Free.

THE TALE OF PETER RABBIT & BURL IVES -- A dance/puppetry production followed a 30-minute Burl Ives program, Sunday at 1:30 and 3:30 p.m. in the Concert Hall. Tickets are $6.50.

SIGN POSTS -- A play about a deaf person who responds to a "Help Wanted" sign, it's performed by the Hippodrome State Theater of Florida Monday at noon and 7:30 p.m. in the Theater Lab. Free.

RADIO PLAYS -- And on April 13 at 10 a.m., there will be a live broadcast from the Theater Lab of the the winners of the Seventh Annual Henny Penny Playwriting Contest on Children's Radio Theater. Free. (Listeners can hear the program on WPFW-FM 89.3). Call 254-3600 for ticket information.