The best way to play with kids, is to forget about your age and play like a kid yourself, i.e., to fully enjoy the games yourself. When we grow up we lose the imaginative power we used to have; you can get away from the trappings of lifes for grown-ups and relive the childtime for a while. Remember, you are not teaching him something; you both are discover something and have fun for that. And it helps if you go down so that your eyes are at the same level.