This will come from personal experience from both myself and my daughter's. When I was growing up in the 80s we used to road trip from south Florida to Louisiana. My mom would get us a paper bag full of cheap toys and car games and give us one from the bag every hour. That worked great for quite a few years.
Now that I am grown and still love to travel we have learned something even better. Don give the kids anything! My daughter's are 12 and have been to 40 states out of the lower 48 and driven them all. When they have their face in a movie or phone, they learn nothing and miss everything. My girls have been road tripping since they were 6 months old and most years go on at least one 3-4K mile road trip. Find games everyone can play and keep them engaged. When they get bored, tell them to look out the window and enjoy the new scenery.
Some games we play:
Alphabet game - use roadside signs and semi trailers. You try to find words that start with each letter. Start with A and work your way to Z. We usually allow X, Q, and Z to be found on license plates or inside words.
Grocery store game. Again work through the alphabet. This time each person adds something the list and the next person restates the whole list. Example: after 4 people you might have "apples, bananas, carrots, dog food", so the 5 person in line would add something from the group very store that starts with E. After 20 letters it gets hard, especially when you have people using odd items, but it's fun and keeps everyone engaged.
One that even small kids can do is roadside bingo. There are tons of reusable bingo boards with sliders. They include cars, busses, signs, animals, etc. My kids have used these since they were 3 or 4 and we still love them. Of course the driver can't participate in this one, but it's fun.
Just don't let the kids stare a screen their whole life.