I am so sorry this has happened. You definitely need a lawyer. Any chance the therapst who are working with your children can help ?? After all - you were sending your son & daughter to therapy and I would think that the therapst involved would have made sure they had the appropriate therapy. Not sure why that woman was yelling at you about making sure when it sounds to me like you did everything you could - and did have them in therapy.
I hope things work out for you - this sounds so over the top for the authorities to take such drastic action regarding your baby especially.