AirPlay functionality is supposed to be much improved with Gotham.
I'm assuming you still have the original Frodo built of XBMC installed on your iMX6.
There is a possibility we can get this to work, but iMX6 doesn't have a DroidBOX approved APK for v13.
What you could try is the following:
Open the Play Store app from Google, and search for, then download: SPMC
Using this, rather than the original XBMC app itself for trying v13/Gotham means if it doesn't work, or there are video playback problems, then we can just uninstall SPMC (which is based on the same source code) and have your original Frodo install of XBMC there the whole time.
Once SPMC is installed, open it up and head to the System menu. Now head up to the Video menu, and then select the Settings level option in the bottom left, and select Advanced or Expert, then select the Acceleration menu.
Make a note of the current settings, then press the Go Back/Return key on your remote, so that XBMC is showing the original Settings menu again.
Head to Add-ons, then Get add-ons. Click on one of the repos, and install a video add-on that grabs your attention.
Play a video using the new add-on. If it works, we'll head on with re-testing AirPlay performance.
If there is no/corrupted video playback, return to the Acceleration menu and try disabling all acceleration methods. If that doesn't work, try turning on one at a time.
Before testing if SPMC (Gotham or Kodi based probably) works better with AirPlay, head to the homescreen of XBMC, then System>Services>AirPlay and make sure at least the first entry is enabled. Whilst here, you may as well check if other remote control options have been enabled. Restart XBMC, and try again with your iPhone/iPad.