In the past pre-order bonuses and items were only received by the adult account. I very much doubt this situation will change in the future as you currently only pay for one set of extras and then you can share the base game.
It would be really good to be able to assign certain extras to a child account - maybe hopefully in the future this could be developed - but because currently financial information and the distribution and utilization of FC Points are involved, and then the situation where the adult account has a different club to the childs account club in-game (meaning it is not possible to transfer non-transferable items between 2 clubs in Ultimate Team) I think the account holder gets everything and that's it.
