The dates against signature can be written at the time of execution also.
Actually all the legal heirs are required to execute the same in person before the landlord, whereas he is giving you the privilege to sign the papers elsewhere, it would be intelligent to utilise the situation instead of arguing about the issues which has no reason or logic.
You should understand the fact that your father was a tenant and not his heir.
Further, this is a pagdi property and not own.
Hence instead of making simple things complicated, better to proceed without making much fuss