The properties whether immovable or movable left behind by your deceased husband automatically devolves on all his legal heirs consisting his wife, children and mother upon his intestate death.
The nominee under insurance policy death claim are just trustee to receive the policy monies and they are required to disburse the claim amount to the legal heirs of the deceased.
Therefore you can send a legal notice to your parents in law seeking your share and your minor son's share in the claim amount and also can file a recovery suit if they refuse.
The registration of property need to be done on all the legal heirs of your deceased husband, so work out a plan accordingly in order to get that registered on your minor child'snname by placing yourself as guardian to minor