OT: Music app for Kindle Fire Kids edition

Sorry this is off topic, but I have my first foray into the world of Android (albeit the "Kindle Fire" flavor). My mom bought my elementary aged boys the new kindle fire "kids edition" tablets (identical to the new $50 model, but with kid features and warranty). Does anyone know of an app & method to get music on to these devices? 

For the most part ALL of my music is in iTunes, so I assume I would have to figure out some way of exporting the music. I do have an Amazon Music account if that matters. 

I have read some threads which talk about this issue, but they are old. They suggest third party apps, so I was wondering if any of y'all have any experience with this? I essentially want to put each of the boys playlists onto their device so that it can double as an iPod. I'm trying to get these set up before Christmas (and the long drive to the inlaws ).