I _want_ ideas like this. I've done a LOT of work with 8x8 LED grids, already. So been there, done that, and can support a student well here. I'll add this to a list of ideas for students who seem like they might succeed well enough to give a shot at it.
I've been wrestling these things through my mind and I'm quite sure that most will not be ready, right away anyway, to deal with debouncing -- whether I/O pin-change interrupt based or timer polling based -- and any kind of state machine involved there. So yes, much needs to be kept 'under the hood' for a while. Yet they need to have the freedom to choose their own project, too.
I do hope that some will eventually want to know how these things may work, underneath. I will let their own interests and questions guide me; I will give them as much as they can handle AND NO MORE. The main thing here is that as soon as they seem to have had enough from me I shut up right away and stop. The key is to listen and take advantage of a momentary interest of theirs and drive through it with some information but only so long as I have their interest. I need to stop as soon as they feel at their own limits of processing and interest and not make it painful to them in any way. They open a door, I start walking through, and I stop just as suddenly when they let me know they are done. Then I do the same, the next time. And so on. They will be my guide as to what they can accept and absorb.
I will not ram anything down their unwilling throats. That is a guaranteed recipe for making people hate education and learning. And is the antithesis of what I'm about.
I'm not sure it's important to even answer that question right now. I'm mostly focused on people who have never done electronics or programming, either one, and who aren't even at all sure of their own desires or wants but who are willing to give it a random shot in the dark just to see if they want to do a little more sometime. It just won't 'click' for some and they won't come back for more. But even then, I want them to take home something that they will show others and have some positive things to say.
This is supposed to be fun and improvisational.
And if someone decides they'd like to push a little more or reach for something just a little harder, I'd like to find a way to accommodate that, too. And be there to help make it a mix of fun and learning with a successful end-point of some kind they can take back with them.
Jon