Ed (15 now) has only just got rid of his little Raleigh which he got when he was 7.
Unfortunately I can't remember exactly which one it was: however no sexy brakes and (vvv important) no gears simplicity is all for kids and cheaper for you, unless of course they are biking prodogies.
Thing is this little bike had two lives 7-9 then he got a proper, very bottom-end mountain bike (he's tall so could just do 26" wheels on an ex-small frame). The little Raleigh was consigned to the garage for for 4 years when it was dragged out pimped by him and became his ragabout street bike until he got a dedicated street bike this year. So it had two lives, and because in its second incarnation it was "disposable" he got into changing parts on it etc. so he got the basics of bike mechanics without totaling his good bike. Oh and finally he sold it to a mate for 25 quid (I think we paid £46). So I would suggest you go cheap and robust, you're probably buying the extras based on your, not a kid's view of a bike.