With a few exceptions, a Google search for children’s organisation logos pulls designs that are clichéd, garish, or overly detailed. Here’s one that doesn’t try too hard and ticks the boxes.
A lesser-known Saul Bass logo, designed in 1963 for the now defunct Transport-a-Child Foundation. Spotted while flicking through Saul Bass: A Life in Film and Design.
I can imagine the shape of the bus changing for flexibility, or kids creating their own vehicles to be used with the black key and wheels, or the key having a little animation.
Simple, memorable, childishly appropriate.
For an insight into the work Bass was most known for, here are a couple of excellent short commentaries on his film title sequences.