Making changes to jewellery that one specified for one's minor children

Person A intends to give some of her jewellery to her 6 year old minor. She then separates the jewellery that she wants to give to the child, from those she wants to keep for herself. 4 gold bangles with design, 1 was allocated to the minor. 4 gold bangles with design 2 was retained.

Person A would now like to make a small change whereby, the minor will have 2 bangles with design 1 and 2 bangles with design 2. Person A will have the other 2 of each design. Can this change be made? If there is a shortfall in value, Person A is happy to pay the minor the difference.

Scenario 2 Person B has 2 minor children, who are the offspring of 2 separate marriages. Person B has allocated some jewellery to the 2 minor daughters. Can any changes be made to this, as the children are still minors, and Person B was not fully aware of the rules of inheritance at the time of the allocation.