My father wants to donate 1/3 of his total property except home as Infaaq (Spending in the way of the Almighty). The idea in his mind is to support a set up or institute like AL-MAWRAD working for the right understanding of ISLAM. My father's query is 'can he does so?'
There can be two implications to your question: a) whether a father can do so ignoring the will of his family sons etc and their needs and b) whether he is right in his thinking that he should donate the money to a organization rather than individual needy persons.
A father has absolute right over his wealth. He can spend any part of the wealth for benevolent causes. He however, should keep in mind that he has to fulfill his obligations towards his relations that he must not be ignoring while doing so. It is entirely his own decision where and how much to spend. He may tomorrow feel that a certain relative of his needs the money more than such an organization and decide to give it away to him. Therefore, we cannot devise a rule for one to follow in this regard. The matter is entirely left upon the person himself -- because it is he who will be held liable before his Lord.