Audible for kids - only possible with Fire tablet or Yoto?

[WaitingRoomBoredom]

DD is 6 and loves audiobooks and listens for half an hour before bed on a tablet. At the moment it is set up using my account which isn't ideal as it's not just kids books and I don't want her buying stuff. As far as I can see, you can only get a kids account if they have a fire tablet.
So, is the only way to get a fire tablet or a yoto? She'd really like a tonie because her friends have them but I feel like she'll grow out of it very quickly and there's not much choice. Are there other audio book providers that are more flexible? What do you use? Any ideas?

My DC have an Alexa in their rooms. They're set up on Amazon kids profile with my audible account so I can control which books from my account they can listen to - this means they don't accidentally listen to psychological thrillers! I think the tonie/yoto options are short lived and lack variety compared to audible.

So you have a subscription for an amazon kids account and they can access Alexa but the content is protected?