I don't know what type of disabilities your little one has but I was looking into this for my grandma when she was struggling to use things due to physical and mental decline and ended up with the "Relish Simple Music Player" which is a dead simple desktop radio with limited controls and preconfigurable presets for FM/dab stations or playlists from a memory card, **but it had no smart features or streaming. ** not really kid optimised but it's good to know there are devices out there that are specifically designed for various disabilities.
As for DIY smart HA based solutions, a compatible device like a google home mini or similar (or any active speaker with a compatable receiver plugged in, or a Sonos One SL or something if you are OK with that) and some simple control device like one of those zigbee scene controllers (like these), the standard spotify integration, plus a bit of automation/scripting or a tiny bit of nodered could become a simple and effective little jukebox.
"Satan, Play Emperor on the living room stereo"