What about some water play, fill up a large mixing bowl and give him a couple of smaller cups and a stirring spoon. Bubbles are always fun, or you could make some playdough? Painting or chalk? Playing with some balls, rolling back and forth inside.

I try to plan one or two things for each play period (eg, between breakfast and morning tea, between morning tea and lunch, between sleep time and dinner) and the rest of the time i encourage the kids to play on their own and entertain themselves (sometimes easier said then done!).