I run a Warhammer gaming club once a week in the evening and I would just like to say....
HIDE ALL THE TIME!!
There is nothing, nothing worse in this hobby than a child whose parent(s) paint the figures for them.
Helping them use the craft knife/superglue etc for assembly is one thing, because there are safety issues, but that doesn't apply to the painting. They could DRINK the paint by the potful and be fine - t'is waterbased for just that reason. (Although I'm not answering for what state everything else would be in if they did :-) )
If they can't/won't/don't want to do the painting (or the rule book reading!) then they're in the wrong hobby. They're either too young for it still or they have the wrong temperament. There is nothing more aggravating than a child who willy-nilly damages other's models because they have no concept of the time and effort they take to produce and ABSOLUTELY nothing worse for a volunteer club organiser like myself (or a store staff member, for that matter) than a child who never gets past that stage because their parent(s) bail them out.
It is a three part hobby - collecting, producing, using - and, to begin with, they need to do all three components, so that they learn the full scope of the system.
The suggested age for the hobby is 13+ - which is why you will have been asked to stay! - although we often find kids much younger are fine. They just have to be fine ALONE!
OTOH - if you live anywhere near Ramsbottom in Lancs, I'll gladly have your DS on Thursday evenings for a couple of hours and he can discuss Orks vs Spacemarines etc to his heart's content.
Just don't tell him he's really discussing and employing mathematical probabilities when he's doing so. That's our secret!