If the property transferred in your adopted child's name is your self acquired property,then the transfer is very much valid and it cannot be questioned by other children.
If the property is ancestral in nature and was inherited by you then you do not have any right to make a transfer of the entire property in your adopted child's name, because you have limited share in the inherited ancestral property which gets divided further among you and your own children equally. Therefore you are entitled to transfer only such portion of land which becomes your own property for the benefit of your adopted child.
The adopted child has full rights after the transfer is effected in his favor by executing a registered document in his favor hence he can very well sell a portion or the entire property for any purpose including to take care of you and your medical expenses. Your daughters cannot question about it nor they can interfere in it.