In my first iPad Gen1 and iPad Gen2 I received a 10W charger. When you plugged in your devices to a lower rated source It would display a msg box telling you the device could not charge from that source.
It seem now the latest update for the iPad minis permits the larger brother iPad2 to charge from the 5w charger.
I will take longer! However you are no longer stranded by a limited division of which charger can charge the apple devices - as they all can, just at different rate now.
Try it yourself and let me know if you charge the 3 and 4 with the 5w iphone ipod adapters.