Answer:
(Fatwa: 1994/1604/B=1431)
Zakah is not wajib on the plot that you have purchased to build home. However, it is necessary to pay the zakah of the amount of fifty thousand that you have kept for your children. Each year you will have to pay 2.5 % as zakah of the whole amount. Qurbani is wajib only on you not on your minor children.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband
