We visit relatives about 650 miles each way for Christmas every year and usually use the car GPS + a Garmin Nuvi with traffic.

This year, we tried something different because I lost our garmin. By the time I discovered, it was too late and couldn't get another one in time.

We mounted an iPad mini to our vents using a Tetrax Xway vent mount and Tetrax Geo vent mount. I normally use the Xway to mount my iPhone to the vent.

We primarily relied on the car's GPS, but this time used Trapster, iExit, and google maps (for traffic). I used the free 200mb data sim from Tmobile for the data, but the coverage was lousy. Next time we will probably just use the Verizon sim and data.

Overall, I would recommend sticking with a real GPS device. At least in the US they are less than $100.