This is a problem with "single-purpose" devices for kids, too. Drawing tablets, music players. They're all actually full Android phones (sans cell modem) and tablets. It sucks.
It represents a general purpose computer on your network which will accumulate vulnerabilities and never be patched or otherwise secured, making it a persistent insider threat as a launchpad for attacks on your network
The issue isn't really Android, it's the touchscreen and the way the UX is a regression from many analog single-purpose devices.
If you gonna have a single-purpose device - make it analog (or close to analog)!
Don't give it a perceptible boot-time and all the other flaws that come with general-purpose computing. Don't make the user have to "wake up the device", let alone have to visually confirm that it is woken-up, before they can switch to the next song.