As parents' groups continue to clamor for better children's TV programming, two critically acclaimed radio programs for kids are calling it quits due to financial problems. This week the Washington-based Children's Radio Theatre and New York's "Kids America," announced their final broadcasts. The nonprofit Children's Radio Theatre, broadcast for 10 years over Washington's WPFW public radio station, will air its final show Saturday. But 26 previously produced half-hour shows will be distributed to public radio stations by National Public Radio starting in January. "Kids America," produced by WNYC and aired by American Public Radio, signs off Jan. 1.