Built a treehouse with my 6yo and it actually didn't collapse
So I decided to surprise my son with a treehouse in our backyard. Spent all Saturday drawing up plans on the back of a Home Depot receipt and Sunday morning we started building. Used mostly reclaimed wood from a fence we tore down last year. The kid was so excited he kept trying to hammer nails before I had the boards lined up right. It's not pretty but it's solid and he actually slept out there last night. My wife thinks I'm crazy but honestly this might be one of the best weekends we've had in a while.
Built one with my kids a couple summers ago and yeah that moment when you realize it's actually standing is pure magic. Your son is going to remember that forever.