Ditto Cat. It's not at all unusual for a kid (even an HG+ kid) to start Kinder without being able to read -- your DS sounds like he's a step up already. He'll probably be firmly in the middle of the pack. And he'll be fine for writing as well. These are not even vaguely "delays", and I don't think a half-decent teacher will think of them that way.
It seems like all you need to do is ask if accomodation for math is possible (as Cat said, it might not be). Science really isn't an issue, because the science taught in K is so minimal. And if something "clicks" for your DS at some point regarding reading, you can address it then. Otherwise, just go with the flow -- I'm sure he'll continue to bloom wonderfully.
