Britannica Kids has multiple quality apps on various topics spanning the subjects of science and social studies. At this moment, this app is a free one and worth your time. (Thanks, Julie Becker, for bringing it to my attention.) It has articles, vivid pictures with captions, and puzzles all relating to the rainforest. The contents will keep the students engaged as they learn about various plants, animals, and landforms of the rain-forests. What a great opportunity for students to explore our world!
(There is a spanish version available at the moment as well.)