That could be a good idea to start with , but as you said "children" , so make sure it's something beautiful and fun so they get it on the first place , I'd like to hear more about the Bitcointalk YouTube channel idea , What are you planning to add there ?
It's never enough to advertise bitcoin , because we are in a war with the other side (banks , media , governments ... ) Media for example try to convince people that only Terrorists and criminals use Bitcoin on the Dark-web which is not true , same goes for for governments just couple of days ago .. Ukraine trying to convince their citizens to use use other payment methods that reserve the user protection and that kind of things ..
PROMOTION! That too on a bigger scale is what we need. We need to educate people and raise awareness that not all people dealing in BTCs are culprits of crime. My best bet is to promote among the younger generations, especially teens, as they are more ready to accept and adopt a radical and new concept. Let the mainstream media pipe their horn.