The "Khan Academy" Android App is not currently available in the Amazon App Store, only the "Khan Academy Kids" app is available.
I was able to figure out how to install the Google App Store and install the full app, however the app can not be added to Child profiles on an Amazon Fire Tablet since it did not come from the Amazon App Store. Unfortunately this means that my children will only have access to Khan Academy when I log them into the Supervisor level account. I did add a direct link to the website on the Child profile, however it doesn't save the login credentials and the browser only displays in landscape mode so it is pretty clunky.
Can the full version app please be added to the Amazon App Store?