@sleepybisexual I generally hate to use Apple devices, but iPod Nano is an exception. To make them work you'll pbbly need a replacement battery and fight a bit with disassembly/soldering/reassembly, but that's also a kid-compatible activity. For a more hackable but pricy alternative check out Tangara!
Anyhow, if I'll have time I plan to write up why walkmans may be an even better option for kids!