The topics that you mentioned don't seem unreasonable for kindergarten, as long as they are being discussed in an engaging, creative way. Children can do a lot more than most adults think they can, and they can benefit a great deal if adults have high expectations of them. The idea in kindergarten is to show kids that learning is fun, and that they can succeed at anything. Learning should be interactive, and hands on, and children should be learning important social skills as much as or even more than academic skills. I am totally opposed to having kids sit at a desk, filling out multiple worksheets for hours.
You should talk with his teacher about your concerns, and try to get a sense of the goals of the curriculum that is used for kindergarten. Find out what the teacher expects from the kids and the parents, and see if you can agree on how much should be done outside of the classroom.