Wow! Your son sounds like an amazing little boy! DD is a little younger than him (18 months) and she has a few sight words but is nowhere near actually reading as far as I can tell.

But I can relate to wearing him out. She's actually in daycare right now where basically she's running/climbing/playing non-stop but before when she was home with me we'd have to get to the park at least twice per day and since we don't have a car she'd walk with me to the grocery store and to run errands too. We also have the late bed time... it's so tiring! Even with daycare we still need to go out at least once in the evening... and she throw a fit whenever we have to go back inside.