I guess it is bad idea to hide any income or money saved or invested for "training" a offspring. Sure, being transparent might make them demand to purchase something, but then educating them about good and bad investments will be better. It will be bad to give them big money before they are mature, but they should at the least know the resources and funds stored or earned for them and for their future by their parents, because death is certain and can come at anytime and all those complications like "hidden money" etc. can cause fights, or a reason for struggle for the rest of the family.