Is zakat obligatory on orphans' wealth (savings and gold) collected from Sadaqat, and are the nisabs for gold and money calculated together? Is zakat obligatory on gold designated for adornment and savings? And is it permissible to give the zakat of one child to another?

Zakat is obligatory on the wealth of each, the son and the daughters, separately. It is also obligatory on the orphan's wealth according to the majority of scholars. Gold is combined with cash to reach the nisab. So, if one's wealth reaches the nisab (which is equivalent to 85 grams of gold or 595 grams of silver) and a full year has passed over it, Zakat of 2.5% becomes obligatory on it. The gold worn by a girl is not subject to Zakat according to the majority of scholars, though paying Zakat on it is more precautionary. It is permissible to give the Zakat of the son or daughters to others, provided that the recipient is among those eligible to receive Zakat. Orphanhood alone is not a reason for eligibility.