A few hours, a bit of driving, some sightseeing, a bunch of walking, way too much talking, and a lot of patience is all it takes to get him to take a nap.
p.s. the car carrying truck hand-me-down from Janet & Tyler is his all-time new favorite. Intricate detail. I thought he was going to burst from joy when I put batteries in, flipped the switch, and it lit up like a christmas tree.