Finally building that treehouse my kids have been begging for

Starting this Saturday. Got the lumber delivered yesterday and watched like three YouTube videos on proper safety. My oldest is 7 and my youngest is 5 so nothing crazy, just a simple platform about 8 feet up in the oak tree. My wife thinks I'm insane but honestly I'm more nervous about my own balance than anything else. Anyone here built one before? Would love to hear what I might be missing.