Your best bet is indeed a mini PC. I think you can probably still find N100 based mini PCs pretty cheap. As for keyboard, you can find a micro 6" keyboard + touchpad (ie K808) for like $25 on Amazon.
As OP said, N100 boxes (at least the ones I have) don't support HDMI CEC natively. So you'll need another dongle.
As OP said, N100 boxes (at least the ones I have) don't support HDMI CEC natively. So you'll need another dongle.