Great job!
One thing people should know if they decide to do this with an iPad, regular or mini, is that you only get true GPS, like what an iPhone has, if you get a cellular equipped iPad. You don't have to actually activate and use the cellular radio, in fact, you can leave it powered off. You just have to pay the extra for the cellular option (can be AT&T or Verizon) in order to get the true GPS equipment.
The regular iPads look like they have location service but it is just based on WiFi routing and triangulation. It is completely worthless for turn by turn navigation.
You could, however, use a regular iPad with an external Bluetooth GPS receiver. Or, I have been able to use a rooted Android phone to act as Bluetooth GPS receiver for an iPad or laptop as well, but that can be a pain in the ass so I would not recommend it if you plan to use Nav a lot.
As far as I know, all Android based tablets are equipped with true GPS equipment, with or without a cellular option.
Also, unless you want to rely on a cellular link to provide the maps, you might consider buying a Nav app which uses maps that are downloaded to your iPad. I travel a lot to places that don't have cellular service and so I use Navigon and Sygic apps. With either of these, you do not need any cellular link, unless you want real time traffic and weather info in the apps.
Also, it is now possible to download a limited area map for off line use from Google for free. This can be useful if you know you are going somewhere without cell service. Or, of you mostly drive in the same area all the time.
In fact, even if you do use a cell phone or a cellular equipped tablet, if you use Google Nav in the same area a lot, like in a particular city, it is a very good idea to download the map for that area from Google. It can save quite a bit of data on your data plan to not have to always be downloading the maps for the same areas over and over each time you use Google Nav/Maps.