for Safe Harbor by Christine Taylor-Butler
Ben and April Webster never knew their parents were scientists on a secret mission until they disappeared. Now what awaits them and their friends is a nemesis so deadly that even Uncle Henry can't protect them. In this science-fiction, adventure novel, the search continues as the group travels from the lost world of Atlantis, to outer space, to an IMAX theater in the Smithsonian. The bond of the diverse friendship is tested against many obstacles as the kids continue to fight to save a universe they are only just discovering. The story is embedded with science, history, sports, mystery, ethics, and culture. Plus there are location codes included that go to real places around the world.
Publisher description retrieved from Google Books.