There are some really good drugs for people with ADD now you have drugs like Ritalin and Adderall
For his bi-polar disorder may I suggest Lithium, Prozac, Depkote, Welbutrin,Pristiq,Cymbalta,Lexapro,Zoloft or even Paxil
As For his mental retardation, a good therapist.
The good news is this kid could easily qualify for the Special Olympics, the bad news is the athletes there have more talent then he does.