No one wears hoods over helmets. Not practical as hood woldn't move when turning head so obstructs vision, too hot and nousy too. Get a balaclava and/or buff neck warmer for under helmets. Hoods on ski jackets are for when no helmet or hat is worn, personally I prefer no hood as it gets in the way when wearing a helmet.
I'd never heard of it either, but a quick Google throws up a German (I think) company called Volcom - all their jackets are helmet compatible. The kids range seems to start from 121 cm tall. Not cheap though! You'd also need to check delivery options with Brexit approaching.