The Kennedy Center's annual Christmas bash continues this weekend with an impressive lineup of acts. On Friday, the Forest Glen Senior Citizens' Choir, The Rockettes of Ages, and the Falls Church 49'ers will perform 20-minute vaudeville- style programs. On Saturday, Tommy Duren and his Supper Puppets will delight audiences of all ages. Showtimes both days are 11 and 1 in the Theater Lab; the programs are free. More free performances are scheduled for the afternoons and evenings, Friday through Sunday. For information, call 254-3600.

One of the more attractive paid performances is Saturday's "Singing Christmas Tree" performed at 3 and 7 by 130 singers, dancers and actors from Greenville, South Carolina. Last year they packed the house with cheering crowds come to see them climb inside and atop a 26- foot tall "Christmas Tree" structure. It costs $3.50, in the Concert Hall. Call Instant Charge at 857-0900.

Chamber-music aficionados shouldn't miss the annual Millennium Christmas Concert at 8:30 Sunday evening in the Concert Hall. For $7.50 you'll hear the Folger Consort and Jubilate perform Christmas works from the Medieval and Renaissance periods, followed by the 20th Century Consort with music by Vaughan Williams and Respighi. Again, call Instant-Charge, 857-0900.