I've downloaded iHud so that we can ensure the jet remains straight and level and check the pilots aren't exceeding the speed limit...
Check it in a turn. I bet it says "wings level".
But is there a cheap moving map that I can also download - so that the tykes can work out what they're seeing out the window?
Get Memory Map. The app costs about $9 but the Australia-wide 250k map is free. You have to download it via the Memory Map program for Windows from MMs Digital Map Shop, then transfer it to the ipad.