Land belongs to grand doughters

the property that your mother had inherited from your grandmother would assume the nature of self aquired property.so you all dont have any claim over it.she can do whatever she wants with the property

I agree with Mr.saravanan sir.

The opinion  of learned friend  Mr. Saravanan is absolutely right. The property acquired gy your mother from her mother will be your mother's absolute property and  she has any and every right to disposed it in any manner and she need not take consent from any of you or any one for that matter. Neither you nor any of your sisters  or even your father has any right to claim any share in the property or in he sale proceeds.  

i to agree with Mr Sravanan, and one more point i want to high light is you said in your query that

my mother sold the land property without our concern, the buyers also wantedly involved in this land by buying

thus the property is registered on the new buyer name and thus any fraud was taken place in the transcation as your grandma is a old person without her knowledge the buyer has played any trick to grabl the property if you can prove that instance with proof then a suit can be filed