Order some joke/fake lottery tickets. One of the ones where every ticket wins $30k. Drop one on his driveway before he heads to work in the AM for him to find. I’ve only done this to two people and they both fell hook, line, and sinker for it. One lady was calling her husband to come pick up the winning ticket to keep it safe.
In my experience 12 year olds are pretty impervious to temperature fluctuations. Little bastards dive into freezing water like it’s nothing and run around in the scorching sun, not even noticing that they sweat through all their clothes.