Thanks so much everyone for the replies. I often feel so overwhelmed and alone... Its so nice to hear from people who have experience in this.

So, here are the educational options that I know of so far. Public school system: grade acceleration and/or gifted program starting in 3rd grade. The gifted program is fully incorporated at a different school in the district and it really seems to be well done. My niece is in the program and it has been awesome for her. Private schools: there are a few nearby, but nothing that I know of that claims to work for a gifted learner. And as far as home schooling, I may be chicken, but I'm not sure that would work out. I have 4 little kids ( he's the second) and our days are not structured or predictable enough to provide a good structured educational environment. I would prefer to make the public school work since we have a neighborhood full of young kids and they all go to school together.
He goes to a short preschool program, 2 hrs. a day, 3 days a week. He enjoys it. He has fun with his friends and he likes the worksheets. He also plays well with his older sister and her friends. I think socially, he'd be ok in either k or 1st.
Again, thanks for all of the advice and suggestions. It gives me more to think about.