I like the bling even less on a full-length unitard than on a leotard, just because there's more of it on the unitard. Why can't they wear leotards or unitards that look like athletic uniforms instead of circus costumes? Also, for modesty I think a leo with separate leggings (either over or under the leo) works much better than a unitard.
The fact that the color change from black to white occurs just below the knee makes me think this outfit would be ideally suited to camouflage bent knees. It made me think of marching band uniforms. If you want to hide kids who are out of phase or unevenly spaced, you put the band in plain black pants and black shoes. If you're confident that they can all stay on the beat and maintain their spacing, you put them in black pants with a white stripe down the side and white shoes to show off their precision.