Built a treehouse with the boys this past month and almost died

We started with like 2x6 boards and some rope. Took forever because every time I'd get something nailed in my oldest would want to 'help' and we'd have to stop. But man when those kids climbed up there for the first time and their faces lit up? Worth every splinter. Still sketchy as hell but we're reinforcing it this weekend. Any of you guys done treehouses before? I want to make sure we're doing this safely.