In the summer, we used to just leave in the morning on our bikes & come home at night. One particular summer, when I was about 8 or 9, a few of us decided to build a tree house in the nearby woods. It was me, my brother (3 years older), and a buddy who was between us age-wise. We'd leave the house in the morning with a machete, a couple of hatchets, hammer & nails, and some rope. Our parents never asked us what the hell we were up to with all that stuff.
So we go about building a basic tree fort. Found a nice spot with 4 trees that were somewhat squared off with forks at a similar height, about 15 feet up. Build a simple platform, kinda like a Huck Finn raft; cut down a couple of small, sturdy trees & get them up going tree to tree, parallel with each other, sitting in the forks. Then cut down a bunch more smaller trees, and lie them on top of the cross-posts. It worked great, and we spent a lot of the summer in that thing.
One day late in the summer, we were all up in the fort together; I think the older two were smoking cigarettes that they pilfered from my dad. We were having a good time, right up until we hear a loud "crack." One of the cross posts broke, and we got a quick lesson on how gravity works. All came crashing down - and of course, the way things broke, we hit the ground, then all the damn trees that were the platform came down on top of us. Not sure how none of us got hurt badly.
Anyway, if I was to see my 8 year old gathering up a machete, a hatchet, and a bunch of other building supplies, I'd damn sure ask what he had in mind.