Instead of threatening to sue them for a civil rights violation, why don't you just do what they are asking to assure them that you are fit and capable of providing a safe environment for the children?
As has been said, they did not take your children because you are disabled, they (ostensibly) took them because you were incapable of properly caring for them. If that was as a result of your disability, then it is certainly valid and not discriminatory. If your disability is of a nature that the children are in danger, then the state has every right to see to it that the children are protected. If you manage to mitigate the danger through medication or some other arrangements, then I suspect you will get the children back. After all, family reunification is the primary goal of any such action initiated by CPS.
- Carl