All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
If this money is still with you, consider which is better. If his children are in need of this money now, then give it to them. If they are not in need of it now but may need it in the future in their education and the like, then you may invest this money in a Waqf (i.e. endowment) whose profit is to be spent on the religious and worldly affairs of the children and offer the reward to your colleague. If they do not need this money, then put it in an ongoing charity like building a Masjid or digging a well.
Allaah Knows best.