Custom Backyard Tree House Play Set

For 2 years my son has been asking to build a tree house. Well, we are in a new neighborhood and there are no trees. I told him the trees will take years to grow large enough for a tree house. We couldn't wait for the trees to grow so we decided to spin it a bit. This is really a play set but if you look hard enough, there is a tiny crape myrtle tree behind it. To my son, that is good enough and it's the best "Tree House" ever!

We spent 2 weekends to design, fetch materials and put it all together. This tree house play set is made from treated lumber. I do have thoughts of stain seal on it but it also kinda looks fine like it is. Is it worth another 3 hours to stain it?

What I learned after building this: 1. Bolts are expensive. 2. It's better to notch posts some so you don't rely on bolt shear strength. It works fine here but for a substantial deck building you should look up notching. 3. On paper, this tree house looked a lot smaller. 4. Kids need to get involved in creativity and making projects become reality. They learn that any idea or dream they have can come true if they work at it.