Sorry this is kind of a late response but I'm on the webdev team at Adafruit, I'd recommend looking at adafruit.com/educators and getting in touch with our support team to figure out the right plan and materials for your class.
Personally I think our Circuit Playground Express boards might be a great fit, they have a ton of useful sensors, a few buttons, and a ring of RGB LEDs right on the board, and they use Python primarily although they can be used as an Arduino derivative as well. Those should keep everyone busy and keep you from constantly troubleshooting a classroom's worth of circuits.
Good Luck! We'd love to hear how it goes!
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