Worldle is not iPad-friendly due to its basis in Java, but Cloudart ($.99) is a great translation of this tool to the iPad platform.
Cloudart has a very simple interface, but with many features that make it useful! Simply copy a block of text via Safari or perhaps from an electronic book in iBooks (many samples of novels commonly used in educational settings are free), or a text-based URL (e.g. the Wikipedia article on any academic topic), and the app will generate your cloud. You can then customize it visually, and even tap to remove or change the emphasis of irrelevant/key words. The cloud can be saved as an image to the camera roll or emailed.
CCSS.ELA-Literacy.RL.5.2 Determine a theme of a story, drama, or poem from details in the text, including how characters in a story or drama respond to challenges or how the speaker in a poem reflects upon a topic; summarize the text.
CCSS.ELA-Literacy.RI.5.2 Determine two or more main ideas of a text and explain how they are supported by key details; summarize the text.
CCSS.ELA-Literacy.RI.5.4 Determine the meaning of general academic and domain-specific words and phrases in a text relevant to a grade 5 topic or subject area.