You have not mentioned how old your child is. If he is younger than 13 then saying on your tax return that he is disabled will not yield any special credits or deductions on your federal tax return. When he is older than 12 you will need to say he is disabled if you need to pay someone to take care of him while you work so that you can continue to get the childcare credit, and later on....you will want to say he is disabled if you are claiming him as an adult so that you can continue to get earned income credit if you qualify.
And....if he receives Social Security--you do not put it on your own tax return. It would only be entered if he has other income and has to file a tax return of his own.