Hi AnotherBookWorm!
You don't need to buy the Little Reader PRO Key, as it's enough that you have valid license keys for the curriculum packs. The only additional purchase in your case is iAccess itself.
Also, you only need to buy iAccess ONCE, even if you own several curriculum packs (and even if you plan to buy additional language curricula later).
After checking out, download the Little Reader Touch app in your iOS/Android device via the App Store/Google Play Store, then follow the instructions here:
Instructions for iOS -
http://support.brillkids.com/entries/21098491Instructions for Android -
http://support.brillkids.com/entries/22665015