How to say legally to father-in-law that we don't want any property from you

There's no provision in law to implement your idea by any prescribed procedure.

You can refuse to accept them if your father makes any transfer during his lifetime or you can execute a registered release deed relinquishing your rights in the property after his lifetime. 

A daughter inherts her share in ancestral property which can be relinquished by a registered deed.

However, father can dispose of his self-acquired property and she (daughter) is not a party to dispose self-acquired property of her father.

When the day comes tell on that day why simply worry today.