In a not-too-far-off suburb of Long Island, where nothing is ever too good (or too much) for the children, some parents are spending up to $100,000 on professionally designed tree houses. There’s enough backyard building that the sub-sub-specialty has its own starchitects, each with his own style: For a young neighbor in Brookhaven named Mackenzie, Michael Ince, a wizard with recycled wood (and fiberglass, for the roof), adopted his signature Tolkeinesque style to the treetops. Donna Karan met celebrity tree-house designer Roderick Romero through a yoga instructor—he built a tree house in Tuscany with stained-glass windows for Sting, too—and ended up commissioning him to build a house for her grandson Miles in a silverleaf maple in Oyster Bay. Long Island native Pete Nelson designed a 120-square-foot tri-level tree palace on a Westchester estate for two preteen girls out of salvaged barn wood. Nelson, the author of Treehouses of the World, is the Johnny Appleseed of the craft, holding workshops (with partner Jake Jacob) and consulting for people who want to try to build their own.