Mentally Challenged and Disabled

Taking care of a mentally disabled child

Q: I am a single mother of my only son who is 29 years of age and is mentally disabled. The reason I am writing this question to you is because he gets a monthly disable grant and I wanted to know if I can use a portion of that money for my personal needs or do I have to ask him or either tell him? And the other is that I wanted to know if I wanted to buy his groceries for the month do I have to ask him or tell him because he is unable to do his shopping by himself?

Mufti Saheb I also request that you advise me accordingly on what is the Shari'ah ruling and the best way to handle this situation and also to make special dua for my son and for myself.