I am a convert (mualaf). Can I give property to my non-Muslim parents through a gift (hibah) or a will (wasiat)?

Yes; although a difference of religion bars inheritance, a gift (hibah) or will (wasiat) to non-Muslim parents is still valid. During your lifetime, you are free to give them anything. Being good to your parents is still required even if they have not embraced Islam. After death, you can leave them up to one third of your estate by will because they are not your heirs. Write the will clearly and keep it in a known place, because your Muslim family may not expect this wish. If you are married, also discuss it with your spouse so there is no misunderstanding later. See interfaith families.