From a teachers point of view just play with him! Read aloud to him but don't push anything, let him just be a little kid, he will be at school for so many years that just giving him your time is enough at this age. I have somewhere a list of things you can do to help your child before they start school if I find it I will post it.
Don't worry, you are obviously a great mum if you are thinking of all this so he is a very lucky boy.