Thanks for the reply, I’ll look at sourcing a battery case and buck converter.
Regarding the buttons, I currently have 8 connected to a single analog pin and using a resistor ladder will read the input to figure out which is pressed, I might end up with 16 of them across 2 pins in the end though. I also have some 74hc165n shift registers that I could alternatively use to the digital pins for them, which might be better suited.