Lusaney don't forget
Gutenberg.org and Calibre (free e-book management software)
Between those two things you can put whatever classics you'd like on the ebook device you choose without having to have wi-fi or hook up to stores or libraries. Simply download the books to your computer (there are other free sites as well.) Then, using Calibre, put the books on the device. Calibre even does conversions from one format to another (assuming no DRM.)
To the original poster, you're asking the impossible. You won't find a color e-book-only reader at ANY price, let alone under $100. You can find Android tablets for that much, or used black and white devices (ebay, etc.) You might consider trying to lock down apps on an Android device, get one that only hooks up via bluetooth or wi-fi and then make sure it isn't available, remove games from the device, etc. The benefit of a black and white e-reader (I like the Kobo original, as it has no touch-screen) is the battery life. My replacement one was only $40 used.