How is the deceased father's rented shop, with an old rental agreement, to be distributed among his heirs (his wife, two sons, and six daughters)?

If your father's lease contract for the shop was under the old rental system with an unspecified duration, then this contract is void because a lease for an unknown period is invalid. Therefore, the shop is not part of your father's estate to be divided. The shop must be returned to its owner, and the contract annulled. As for your father's belongings in the shop, they are included in the inheritance and should be divided among the heirs.