What do your kids who tend to get carsick easy do on long road trips?
Blanket/sheet for seats, dramamine, plastic bags, clorox wipes, roll of paper towels, extra change of clothes and patience. It never fails for my oldest to get car sick on longer rides.
Mattress protector or a water proof car seat cover (also put one on the floor). Hydrolite drinks to stay hydrated. No devices or books. And there are child safe medications they can take but otherwise ginger is a good one that can help settle tummies. Usually in lolly form unless they like the taste of it. Keep foods light and easily digestible. Most kids outgrow it, between the developing vision and middle ear its common but if its severe talk to the doctor to have eyes, ears etc checked out. The other thing that can help is window shades and try to block their line of vision between the two front seats (just dont block drivers ability to use mirror). Kids long distance vision is still developing and watching things zoom past is too much for them.