Is it permissible to donate a house as a perpetual charity (Sadaqah Jariyah) to be used for the care of orphans after one's death, if the family agrees and is not in need of the money, and would this compensate for not having a child to pray for the donor?

If the house does not exceed one-third of your wealth, you may bequeath it to be an endowment (waqf) after your death, and the heirs have no right to object, nor is their permission required. However, if the house exceeds one-third, you are not permitted to bequeath all of it as an endowment, because a bequest is not valid for more than one-third. Scholars have differed on whether a bequest exceeding one-third is void regarding the excess amount, or whether it is contingent upon the heirs' approval. The majority view is that it is contingent upon the heirs' approval. The heirs' approval of the bequest is only considered valid after the death of the testator and their entitlement to the inheritance; approval before that holds no value.