Dec. 25: Christmas Cabaret with The Holidays and Gino Washington at Ernie D's Campus Ballroom, Petoskey at Fenkell (nr. Liver- nois), 9:00 pm- 2:00 am, $4.00 at the door, B. Y.O.B. Dec. 26-28: "Ebenezer is a Geezer!", children's play at the Youtheatre, for more information, cali 833-7900. Jan. 11: A f ree folk-blues guitar Workshop at Music Strings N1 Things, 1801 S. Woodward Birmingham. Starts at 12:00 noon. 642-5536 Jan. 14: Howard Kohn and David Weir, Associate Edltors of Rolling Stone, authors of "The Inside Story"speaking on the Patty Hearst story and the "Underground, at the Showcase Theatre, 8:00pm, $2.00 by mail order or at the door. Jan. 10-Feb. 12: Paintings of George Ortman, at the Gertrude Kasle Gallery, 310 Fisher Bldg. Everyday: The International Afro-American Museum at 1553 W. Grand Blvd. exliibits Black history & achievements, 9 am to 5 pm, Mon.-Fri. (except Dec. 25 & 26 and Jan. 1 & 2). Cali 899-2500 Ice Skating at any of the City's 12 artificial skating rinks, $.50 for children, for locatlons and hours, cali the Recreation Dept. at 224-1111 or 224-1100. ANN ARBOR Ann Arbor Civic Theatre, 201 Mulholland, 6627282. Jan. 17 & 18, Dylan Thomas' "UnderMilkwood", 8pm in the studio. U of M Professional Theatre Program, MendBlssohn Theatre (Michigan League), 7640450. Jan. 16-18, A new American musical "The Robber Bridegroom", 8pm in the Power Center for the Performing Arts. Matinee 3pm on Sunday. Performed by the City Center Acting Co.