It has become the most natural thing to do: get in  the car, type a destination into a smartphone, and let an algorithm  using GPS data show the way. Personal GPS-equipped devices entered the  mass market in only the past 15 or so years, but hundreds of millions of  people now rarely travel without them. These gadgets are extremely  powerful, allowing people to know their location at all times, to  explore unknown places and to avoid getting lost.
But  they also affect perception and judgment. When people are told which  way to turn, it relieves them of the need to create their own routes and  remember them. They pay less attention to their surroundings. And  neuroscientists can now see that brain behavior changes when people rely  on turn-by-turn directions.

Washington Post article
by M.R. O'Connor, who wrote
Wayfinding – The Science and Mystery of How Humans Navigate the World

I haven't read her book (yet).

I think GPS is a great tool for explorers, but prefer to glimpse at the arterial roads from a map, and see where there are nearby points of interest, and supplies.

I generally only use location-aware GPS to find specific addresses on side roads.

The traffic redirection thing can be useful in cities, but be forewarned about using it in the country. Some of the apps that are looking for shortcuts may take you on long / bumpy dirt roads. If you have a car with no clearance you'll be driving 5 mph.

Side note: Check in with park rangers – they are your friends. They know parks better than almost anyone.  They will tell you good options for your group, and warn you about fire safety (!!!).