I've mentioned this before, but earlier this year I saw a woman riding one on the main road by Park Place/St James Place with presumably her daughter standing in front of her on the footplate. The kid couldn't have been more than six years old, no helmets, and traffic was fairly heavy. When the woman realised I'd clocked her she looked horribly embarrassed. I don't know if she thought what she was doing was illegal, but she clearly knew she shouldn't have been doing it.
Shit like that would have got child services involved years ago, it's endangerment.