More ideas from Veroni
could use lattice om sides of upper level and maybe a lattice vertical up one side (get Martha to plant a vine)

This is a really nice tree house it has windows and is fully closed for imperfect weather when the kids want to get away.maybe put a tv inside

Cedar Stage Treehouse - Modern - Kids - boston - by Living Edge Treehouses & Edible Landscapes

Cedar Stage Treehouse - Modern - Landscape - Boston - by Living Edge Treehouses & Edible Landscapes - lower level

build a small deck around trees in the backyard

we have been trying to come up with an idea around the trees towards the end of our yard. "If you have a leveled yard and trees, try this awesome DIY project. People of all ages will enjoy this mini sun deck.