This is the weekend, Satuday through Monday, when Wolf Trap will be hosting its seventh International Children's Festrival. The hours are from 11 a.m. to 5 p.m. and all over the nation's first national park for the performing arts there'll be action for the small fry.

It's international because various embassies contribute performers. This year's nations will include Canada, Venezuela, Ireland, Finland, Korea, England, Sri Lanka, Morocco, Israel, Japan, Norway, Sweden, Denmark, India and the Philippines.

Some of the performers are local favories: mime Craig Babcock; WRC-TV's Beth Arnold and Roman Paska, of "The Beth and Bower Half Hour"; the Pupppet Theater's Lynnie Rabuck; Michael "Joe" Baker; Lynner the Clown; the Blue Ridge Players; Glen Echo Dance Theater; Virginia Crabgrass and Teresa Cordova.

Groups will include the Contemporary Dancers of Winnipeg, Richmond's Theater IV, the Vienna Ballet Company, the Southwest Soul Sisters, the Palisades Theater Company, Mount Vernon High's "Once Upon a Mime," the Connie Teachout Dance Academy and Mt. Lebanon School of the Dance, repressnting Middle East dances.

That's leaving out a lot of individualso and groups, sponsored by the Fairfax County Council of the Arts, the National Park Service and the Wolf Trap Foundation. Tickets are $2 per person, obtained at the gate; details at 941-6066.

Another special is coming along for the Kennedy Center: the Honolulu Theater for Youth, which will open the free Children's Arts series Sept. 8 with "Tales of the Pacific." Wallace Chappell's note company, in its first mainland tour, presents his collection of Pacific folklore to an original score by David Choy. Performances Sept. 8 and 9 will be for school groups. General peformances will be given Sept. 10 at 10:30 a.m. adn 2:30 p.m.

Kary M. Walker, who as co-founder and co-producer for Harlequin Dinner Theater was a critical force in setting its enviable standards and atmosphers, has resigned to become managing director for the new Weinberg Center for the Arts in Frederick, Md. This is in th former Tivoli Theater just off the Frederick square, a 1,200-seat auditorium built in 1926. The Dav Weinberg family has donated the theater to the city for the Arts Council of Frederick City and County.

Walker's immediate challenge is to line up "the widest panoply of attractions" to fit all tastes. The Kennedy Center's Ray Brubacher recently restored its pipe organ, which will be used for a coming silent film series. Texas-born and educated, Walker was in Vietnam with the Army and served as musical director for various Texas productions befor befcoming Harlequin's co-founder in 1972.

Wednesday, Sept. 7 will be "Irish Theater Day" in the Kennedy Center's free symposium at noon in the AFI Theater. Taking the podium will be Olney's director James D. Waring of "Philadelphia, Here I Come" and two of its Very Irish leads, Pauline Flanagan and Helena Carroll, all of them gifted with Irish gab.

"Purlie," which the recreatin department's Ward VIII Youth Community Theater has been touring in the area the past two months, has two September dates: this Saturday night at 8 at the Carter Barron amphitheater and Friday, Sept. 16 at 7:30 p.m. at Shaw Junior High auditorium, 7th Street and Rhode Island Avenue NW. Juniene Poulard directed the musical with a cast of teens and adults.

"Sweet and Hot: The Songs of Harold Arlen" continues through Sunday at the New Playwrights Theater Kevin Hall has returned to the cast; details at 232-1122.

Charles "Honi" Coles, Marilyn Johnson, Bettye Lavette and Dolly Lauria are in the cast of the touring "Bubbling Brown Sugar," which returns to the National on Sept. 13 . . . TV's Virginia Graham will be in Hayloft Dinner Theater's "Any Wednesday," whichfollows its Vegas revue, "Bottoms Up," ending a summer run on Sept. 18 . . . The Oxfor University Presss is starting a promising series of books with Gerald Bordman's "A History of the American Musical Theater." Coming soon will be others on "Show Boat," Jerome Kern, and Harrigan and Hart . . . Tony Raiford of the Maryland School of the Ballet has received permissioin from composer Stephen Sondheim and writer Arthur Laurents to develop their "Anyone Can Whistle" into a ballet work. In 1964 this one about a mayor and his wife was ahead of its time, but revival rights are not presently available . . . Andrew Kelly, who did his doctora at the Folger Library, has joined the new communications department of Princet's McCarter Theater Company.