I have a 2nd grade niece that has a considerable visual impairment. Simply put the text in books is often too small for her to read and this is causing trouble with her reading progress. My sister and husband are considering an iPad or a Kindle Fire to help her read as she loves books. I am mainly interested in which product has more features for increasing text size in a manner that would be most beneficial to helping a visually impaired child. "text to speech" features are less important. As much help as possible would be great. If you could detail the features of why the iPad OR Kindle would be better, you'd be helping out a very special child. Thank you!