Five Little Gefiltes By Dave Horowitz G.P. Putnam's Sons: 32 pp., color illustrations, for ages 4 to 8, $12.99 What Leo Rosten's "The Joys of Yiddish" did for adults, Dave Horowitz's "Five Little Gefiltes" might do for kids: introduce people of all cultures to Yiddish, in all its kvetching, shvitzing glory. The plotline is simple: Mama despairs as, one by one, her five children -- who look like matzo balls made out of fish -- disappear from the jar of Bubbe's Homemade Gefilte Fish. They've gone to the theater (where "Little Miss Matzo" is playing) or to the deli ("such chutzpah"). It's a baby borscht belt in a book, so enjoy already. Each charmingly illustrated page not only tells the tale of the wayward kids, but also is plastered with little in-jokes from the Lower East Side of an era when a dozen eggs cost a nickel and a jar of schmaltz was just 2 cents. Adult readers may need to sneak an advance peek at the helpful glossary -- if they need a shmear of help explaining this meshugana language to their young audiences.