I don't but I wish you luck. I still have fond memories of the one Dad and Grandpa made me in the mid 70's. Mine was only a 4x8 sheet of plywood about 8' up in the tree with an old pulley mounted above it with a rope so I could haul stuff up. I was the king of the world. Your boys will love it no matter what it is.
Lordy, there was a giant oak tree out back of our school when they did an expansion to it. As the workers removed forms and we collected the material and hauled it up the tree. I was in the 5th grade and it was an 8th grade tree house. Never got to climb the first step.
The county put in a playground behind the school and I watched some fool kid girder that tree as work was being done above him. 9 rooms came tumbling down over the next 2 years.
Add a bit to my first entry.
I was riding my bike in the neighborhood and spotted Steve hammering 2X4's to a tree. Hey, what's you doing? I want to build a tree house. The first 2 doable limbs were 20 ft off the ground. Then Aimee the younger next door neighbor came out and asked Steve how it was going. I fell
in love with Aimee, yet a lot of years younger than me at the time. We went to the school and collected material to be used on the treehouse. We used 2x4's and 3/4" plywood for the floor. Almost squared we use 1/4" plywood glass crate material for the roof.
Got the last piece of roof on as a storm rolled through. Aimee hung onto me for dear life.
A friend's younger brother married Aimee. When we met years later she whispered in my ear, you never returned to the treehouse.
My son bought a hardware kit for a swingset made of wood. Then buy the wood. It was doable for about 12 years until he moved and took it with him. At the back of his place is a fallen tree that's still alive. The granddaughters can run up the tree about 30 ft off the ground. We've collected other used playground wood to add to what he has from craigslist and county swaps and sells for free. They have a 10X20 house on stilts with a tree to come down or a knotted rope.
8 and 5 years old they are ready, but mom says no for an over night thing.
cs, on the 2 trunks on the left I would bolt a 2X6, 2X8 to them, the length would be up to you. The height would be up to you. Go out from the tree and plant 2 4X4 post. Plant them square with the 2X6/8. Get them long enough for walls. Frame that up and floor it. Frame the walls and roof. 4 to 5 ft studs is plenty. If you use plywood siding with a 4 ft wall can cut sheets in half. Roofing material would be up to you. Roof pitch would be up to you. Add a small window to the front and rear or just a square hole. A door or doorway can be added between the trunks.
Between all the trunks build a platform so a ladder can go in the center. Add rails a few ft up.
I’m thinking about going a couple of hundred yards into the woods behind the house and building a free standing tree house that would double for a deer stand. There just isn’t a tree where I’d want it.