Couple of suggestions that can be tedious, but might as well exhaust them if you are still stuck.
-When you import sounds into Construct try setting your encoding quality to the lowest first: 96kbps (lowest quality, quickest download.
Still no luck?
-Download Audacity. Save some of your native files as .wavs at 44100 bitrate from Audacity. Now try Round 1 again importing your new wavs from audacity.
Still, Still no luck?
-Let's test your Ipad Mini to see if it can play ANY sound exported from Construct2.
Make a new Construct file, import sounds from the free bundle that comes with your license. Make a button, etc. to play a sound you imported. Test to see if you can hear any of those when played on Ipad. If you CAN hear the bundled sounds, then it has got to be something with your source audio files or maybe an event in your actual file. If you CANNOT hear even the bundled sounds then the problem is bigger than just your one source file with that Ipad mini....
Granted, IOS is problematic. I've pulled my hair out a lot over the sound issues for device playback. But it is possible to get sounds to work. I use an ipad mini for testing as well and got sounds to work. However, I am using Cocoon for export, so we are a little different in that regard. Maybe I'll experiment on my mac to play natively without a wrapper.
Good luck and see if any of the above work for you. Keep at it.