Though it's entirely possible to simply walk around the lodge to get to the tree, the elephants habitually walk through its center, at which time the employees are careful not to approach them. With calves in tow, they're (almost) like any other group of tourists taking a family vacation.
While these elephants roam without problem through human areas, not all African elephants have such positive interactions with humans. Poaching for ivory has decimated populations in the past few decades. See this page for more information and how you can help save Africa's elephants.