1) once gift deed is executed by mother in favour of son then son would be absolute owner of property
2) on son demise widow could not have sold the minor share in property without the court consent
3) A transferee of such an alienation does not acquire any interest in the property. Such an invalid transaction is not required to be set aside by filing a suit or judicial proceeding. The minor, on attaining majority, can repudiate the transfer in any manner as and when occasion for it arises. After attaining majority if he/she transfers his/her interest in the property in a lawful manner asserting his/her title to the same that is sufficient to show that the minor has repudiated the transfer made by the defacto guardian
4) best option is to cancel the sale deed
5) mother should obtain permission from court then sell the property