Is it permissible to give usurious money deposited in a bank account to someone eligible for marriage without informing him, or how should it be disposed of?

Dealing with riba-based (usurious) banks is not permissible except out of necessity, and necessity is measured by its extent. There is no necessity as long as it is possible to open an account with an Islamic bank. What is obligatory is to repent from dealing with riba, to deposit funds in an Islamic bank, and to dispose of the usurious interest by spending it on general Muslim welfare or by giving it as charity to the poor and needy.