I felt a bit like this with my son, but he went to a montessori 3 mornings a week when he was 3.5 yrs and that meant he had to concentrate there,and i could be the person that played outside with him. All nurseries must get children to play outside some of the time, but if they need to run around a lot then a large open space is the best. They have got to learn to concentrate before they start proper school. Have you tried playing squash with him? this is a great way of tiring them out ( obviously you do not play to win, just to exhaust them).