The Easter film openings will include two fairly promising attractions aimed at family audiences, "Raggedy Ann & Andy," a new animated musical fantasy supervised by Richard Williams and scored by Joe Raposo, and "The Littlest Horse Thieves," a live-action melodrama produced by the Disney studio about three children in a Yorkshire mining town, circa 1909, who resolve to rescue pit ponies earmarked for extinction.

Williams is probably best known for the credit sequences that adorned - and sometimes outshone - such movies as "What's New, Pussycat?," "Casiono Royale," the "Pink Panther" series and "The Charge of the Light Brigade." Raposo became famous as the music director and principal song-writer of "Sesame Street."

Originally, "Raggedy Ann" was planned as a TV special, and Raposo composed the score before the backers (ITT, the parent company of Bobbs Merrill, which publishes the "Raggedy Ann" books) were persuaded to attempt a theatrical feature and recruited Williams.

Williams in turn recruited some vintage talent: Grim Natwick, who had worked on "Betty Boop" cartoons for Max Fleischer and on "Snow White" for Walt Disney; Art Babbitt, who helped create the character of Goofy and worked on "Fantasia"; Gerry Chiniquy, a specialist in "dance animation" at Warner Bros. At any rate, the graphic and musical aspects of the project would appear to be in good hands. The crucial question may be the ability of screenwriters Patricia Thackray and Max Wilk to extract an effective scenario from Johnny Gruelle's rather sedate material. The movie opens Wednesday, March 30, at area theaters.

"The Littlest Horse Thieves," arriving Wednesday, April 6, at area theaters, was directed on location in Yorkshire by Charles Jarrott, a new hired hand at Disney with a less than enthralling list of credits - "Anne of the Thousand Days," "Marry, Queen of Scots," the Ross Hunter "Lost Horizon," and "The Dove." However, the story was written by Rosemary Anne Sisson, who worked on the unusually sturdy and gritty screenplay for "Ride a Wild Pony," a recent Disney production shot in Australia. The most prominent member of the cast is the late, unforgettable Alastair Sim, who plays a mine owner.

The local opening date for George Roy Hill's "Slap Shot," starring Paul Newman as the play-coach of a struggling minor-league hockey team, has been postponed a week to Friday, April 1, at the K-B Fine Arts. Bryan Forbes' Cinderella spectable, "The Slipper and the Rose," has been dropped from the Easter list and now appears to be drifting somewhere between summer and limbo, "Demon Seed," a sci-fi thriller with the possibly horrifying, possibly ludicrous notion of Julie Christie as the love object of a sex-starved supercomputer, is due at area theaters on Mar. 30.

K-B has announced a festival of ballet films at the Studio 2 beginning Wednesday. The opening program highlights The Royal Ballet with Margot Fonteyn. The remainder of the films are Soviet productions, all but one featuring works and stars from the Bolshoi and Leningrad Kirov companies. Pattie Fabrizio will handle inquiries about group sales at 244-7700.

Unless one of them is persuaded to drop out of the competition, it appears that Robert Redford and Steve McQueen will star in rival movies about Westerner Tom Horn this summer. Since the business and public stand to gain more from major stars competing at the same character and competing at the same character and genre than declining to work at all, here's hoping that neither abandons his movie.

United Artists is backing two pictures about truckers: Norman Jewison's "F.I.S.T.," written by Joe Esztheras and starring Sylvester Stallone, and Sam Peckinpan's "Convoy," reuniting the director with Kris Kristofferson, Burt Young and Ernest Borgnine. The former, a far more expensive project covering three decades in the evolution of a truckers' union likely to be interpreted as the Teamsters, is scheduled to begin production May 9 in Iowa. The Peckinpah film starts a week earlier in New Mexico. Peckinpah's last production, "Cross of Iron," an adaptation of a German war novel made on location in Yugoslavia, should turn up among the summer releases.