Cathy -
You are so far ahead of the game than I was. When my son was this age I was still in the thick of denail! Sure my son was bright, like all the other folks in my family and friendships, but he'd be fine, right?
You are in great shape, because when damage starts happening to your son, if he is vocal, then you will know what to do. When the school started noticing that something was "different" about my son in 2nd grade, it took years to get things right, because I went chasing butterflies in so many directions first! It really didn't dawn on me that school could be a dangerous and damaging place for a gifted kid when they get to be the top half percent or more extreme. The school thought that there was something wrong with him, so I believed them.
Also, some kids get to school and are so obviously advanced, that the parent doesn't have to fight that much. Lots of it depends on the child's personality. I think it's great that you'll be doing the EPGY at home.
Have you actually spent time observing in the various possible kindergarden classes? I know it's a risk, but if you phrase it as "I'd like to see for myself how my son's maturity level would be in a K classroom" as if you are thinking of Redshirting, perhaps it would not be a problem politically?
Best Wishes,
Trinity
