But I want to know if my family would get any help from Social Security after my passing.
yes, Social Security can help your family if you have earned enough credits through your work.
Do you also know about if ever the adult child is already receiving disability benefits in his own record, can he still get benefits on my record?
He still should check if he can get benefits on his parent's record. Higher benefits might be payable and he could be entitled to receive Medicare.