TJ is right the radio is not legal in competition – However, it is legal for every other on track practice session and is one of the most powerful training tools if used correctly and by someone that hopefully has some kart racing experience.
I see many dads coaching (and I use the term loosely) their kids and they’ve never even say in a racing vehicle of any kind. Needless to say, they’re the ones screaming at the kid over the radio the whole way round the track.
I sell Two-way radios for a living and don’t get me wrong a sales a sale. But when your son is 6 years old he should be practicing by himself trying to gain confidence and once you stick com’s in his ear he will be looking to hear advice every lap and could actually become a safety concern.
As a parent i would stay away from com’s while he’s on track it will do more harm than good for a 6 years old. I would just stay off track when there are drivers going twice and three times faster.