If you think you might want a GPS device, consider an iPad with cellular service. Only the cellular ipads have GPS, and they're really good for it; large enough to show a decent size portion of a map, while small enough to easily be placed in the passenger seat of a car. GPS is the main reason I got an iPad mini with cellular.
The main reason for getting an iPad mini 4 instead of a mini 2 is it's likely to be able to run the latest iOS and software acceptably for a longer period of time. Right now, while the mini 4 is a bit snappier, the mini 2 works great. But you'd probably be able to keep the mini 4 longer without being tempted to upgrade. Another reason for getting the mini 4 is it has decent external speakers. They're not great, but they're far better than the mini 2 which are way to soft to be very usable. In your shoes getting a new device I'd get the mini 4, but then I make great use of my mini.