Hawzah News Agency – Imam al-Rida peace be upon him said:

مُرِ الصَّبيَّ فلْيَتَصدَّقْ بيدِهِ بالكِسْرةِ والقَبْضةِ والشَّي‏ءِ وإنْ قَلَّ، فإنَّ كلَّ شي‏ءٍ يُرادُ بهِ اللَّهُ - وإنْ قَلَّ - بعدَ أنْ تَصدُقَ النِّيّةُ فيهِ عظيمٌ.

'Instruct the child to give charity with his own hand, be it a piece of bread or a handful of [food] or any other small thing, for everything - no matter how little it is - if done for the sake of Allah and with an honest intention is great.'

Source: al-Kafi, v. 4, p. 4, no. 10