Hi J.,
I am not the mother of a special needs child as you are so I can't say I know at all the struggle you're having in your decision regarding your son David and the best way to educate and further his progress. I wanted to offer you some encouragement though when it comes to depending on the public school system for support. I have my degree in Elem. Education and have taught normal classes. I have had the opportunity, however, to work on several occasions with special education classes like you are describing and I have been so impressed at the diligence and love I've seen special education teachers show to their students. I think we are blessed to live in a country that doesn't see these children as "throw aways" and just institutionalize them as so many others do. On the contrary, we pay taxes to a government that believes the special need children and adults of this nation have the same rights as healthy minded children and shows that through funding excellent programs and classrooms to see these little people reach the highest potential they can. So, I say, go for it! Put him in, give him a chance to socialize with other teachers and children, let him be introduced to new therapies and programs that these highly trained teachers will know about. It would probably do so much good for you as a family, too, to know that you are giving your son a chance to experience a little piece of the world outside of all of you guys.
My sister has a very special needs child, too, not CP, but she is and always will be considered MR and will never be able to live independently. She will not officially be ready for kinder until the next year but has been doing preschool through the Easter Seals. My sister says it has been such a blessing, they do so much with Abby, things my sister could never have enough patience for.
Best wishes with whatever you decide, just remember that old phrase, "it takes a village to raise a child" - that is true for special needs children, too. Build a great relationship with your child's special needs teacher, and you will be so happy with the decision to share him with others that will help him and you, too.