You should give the same interest money to your poor relative without the intention of reward. He may spend it as per his needs anywhere he wishes. He may buy Fazail Amal as well.
سبيل الكسب الخبيث التصدق إذا تعذر الرد على صاحبه (شامى).
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband