"Kidsongs." Warner. $19.98 each. The concept is sound enough: making music videos for children, using such classic songs as "Ring Around the Rosie," "Old MacDonald Had a Farm" and "London Bridge." Each of the four (eventually to be 10) 25-minute "Kidsongs" tapes strings together 10 to 12 such tunes with a cohesive if innocuous theme. But the musical execution is bland, the visuals equally unexciting and, while lyrics are included, no effort is made on the tapes themselves to encourage singing along. A more resourceful challenge to kids' passive viewing habits is needed.