Firslty, whenever we are going to buy any property we should inquire a little about the same.
Secondly, go to the registrar’s office, and inspect the records of the land as to the chain of all transaction with respect to the same property after paying nominal fee of some Rs.
Thirdly, as per discription of the property, it seems that it is self acquired property not the anscestral one where children can claim their right.
Fourhtly, but, still as the property was not Will to the wife which means children would also have right as their father died intestate (without a Will) and they have right as per Hindu Succession Act.
Fifthly, so please tell them to relinquish their right to their mother first only then you would buy the same otherwise even if they give the consent still they can deny the same in the future.
Rest you are free to ask anything over phone or email through Kanoon.