Stores are full of CDs for kids. . . . Parents might want to check out this latest from the bargain Naxos label. Here are 27 pieces based on Hungarian and Slovakian folk songs - all simple, angular and attention-grabbing, some invigorating, some calming, and some, like a Hungarian "Play Song," quite beautiful. Jando, a Hungarian pianist, gives them a good rhythmic bite. Kids will like the sharp, succinct tones and maybe - who knows? - want to try to play them themselves.