Every kid is different. My wife and I decided that we wanted to have some sort of activity, what ever it was, so that he could learn from other adults. We didn't care if it was sports, or music, or scouting, or 4h, or whatever. He chose scouts, and he went through to eagle. Our pack/troop owned their own camp land, and I made sure that my wife and I did more than drop the kid off at activities. Was it perfect? No. Was it good? Yes.

I would suggest an updated orienteering. Using mobile phones or hand held GPS's to go Geocaching, but maybe punch it up a bit with some kind of clue to cache 2, 3 and so on. Would definitely take some pre-work, but they'd learn something about Latitude and Longitude...

I'm dealing with 2nd to 5th graders. Can't get too complex

Dude, have you watched a 3rd grader with a phone lately :-)

Must be a really clean kid. Hope the deer is not allergic to soap.