I'm planning something like this. I already have Home Assistant with Music Assistant working, so playing radio and music and audiobooks in rooms are already possible with my phone. I plan to add ESPHome device with NFC reader to trigger plays so it's easy for the kids to use it. Just need to find where I left my roll of 50 NFC stickers.

One suggestion: In my opinion, kids nowadays are very familiar with charging devices with USB-C. Powering the device with USB-C will be much easier. Worse case scenario, I'll use some small portable power bank and place it inside.