I love a good treehouse and if kids are gonna play pirate, it's as good a place as any. Okay, maybe not quite so good as the beach, but maybe animal pirates are different. In fact, I'm sure they must be.
Our neighbors, growing up, had a treehouse of sorts. They built multi-leveled rooms between 4 telephone poles over their backyard sandbox. From this I learned that outside gets very cold at night, even in summer. And don't play in the sandbox if cats live nearby.