That is super cool! I really want to learn to design a simple PCBs (not really sure if a keyboard qualify) and do not know how/where to really develop that knowledge being complete out of any hardware related stuff at work.
I think a small PCB with 4 keys is not a bad beginner project at all especially if the keyboard side really motivates you. Check out Ruiqi Mao’s keyboard PCB guide for an excellent tutorial on doing just that. Also see our Awesome-Electronics list for more links and tidbits.