Well, this morning the Neo Alphasmart and the iPad Mini would not pair any longer. The Problem seems to be with the Alphasmart rather than with the iPad, as it just goes to the file and does not recognise the iPad Mini (though it could also be that there is something on the device that blocks the signal from the USB port). But whatever may be the reason, it did not work this morning. Too bad.
3/27/2013: It works again. It seems that the iPad is particular about the order in which you connect the Alphasmart. In other words, you have to hook up the USB hub first and only then connect the Alphasmart. Furthermore, not every USB Port on the hub works. No idea why, but I tested it several times (and one does not work, the other does).
4/1/2013: Using another (cheaper) unpowered USB hub works flawlessly. (Perhaps the whole thing is finicky about the exact nature of the hub.)