Thanks for joining the jam! We are glad to have you:)
To answer your question- If you prefer to make a game with a single input rather than the P300 controller we have distributed that is 100% A.OK! We can use a different input method to have our children play your game without relying on the visual stimulus. So in that case we can definitely work with what you provide! (Right now we actually exploit this input method with an online knock-off version of Super Mario Brothers to play with some of our kids. We control the left and right movement, and they jump with the BCI controller).
This said, part of our draw with the P300 is in that there is a clear delay built in with the P300 that the user can see and expect. This same delay happens with the other input scheme (e.g. for single button inputs) but the delay/timing aspect is a bit less clear. On the plus side though we will be working with you (and other developers!) throughout the jam to try and help you make the best game you can and understand how these delays could be considered in different game design elements.
Hope that helped some! We are working hard to put together a Discord so that the participants who aren't in the Calgary/Edmonton area can chime in and ask us questions throughout the jam. Let me know if you have any more questions! Cheers.