How to get the muslim ancestral property if son is adopted

Respected Lawyers, I have a situation here, Expecting your guidance. My father is adopted son of my Grandmother. But almost no evidence for that. She has few sents of land in Tamil Nadu, We thought it would come to our dad, After get to know Muslims law, It seems not possible. There is no legal right in land for adopted children it seems. the property will go to only their kins. Our grandma is willing to write that to us. So some suggested that the cleaner way would be sell it and buy it. So we decided to do like that. Unfortunately in TN there is some case going on which doesn't allow an unregistered land to sell. So it is completely blocked situation. Recently they say that case hearing will be on 30th of january 2017. My grandma is getting sick day by day. Is there any proper solution get land ASAP ? Thanks