Addressing this issue, Dr. Monzer Kahf, a prominent economist and counselor states:

“Zakah is due on the estate according to several schools of Fiqh and many scholars because Zakah is a duty that does not die with the passage of time. This means that paying it out of the estate is one of the first requirements from the heirs, especially children. If some of the heirs did not do that, a good child doing it would remove InShaAllah at least some of the sins from the neglectful parent and be undoubtedly rewarded for the child too as we are told by the Prophet Muhammad (peace and blessings be upon him).
In general, any good deed done by a child with the intention of benefiting a deceased parent is InShaAllah accepted and good including charity.”