Of course, you have the option of withdrawing your savings from your account for your children. But we do not recommend this as it is not in line with the aim of saving.
However, if you do decide to make a withdrawal: Transfer the desired amount from the piggy bank to your main Clanq account. You can withdraw as much from this account as is available. Alternatively, you can also transfer via IBAN to an account at another bank and withdraw as usual.